Remove FluentValidation; validator/DI cleanup (#7)

## Summary
- Remove FluentValidation dependency; replace with plain IModelValidator<T>/ValidationResult pattern (ported from BuyEngine's Guard/validation approach), wired via a ModelValidationActionFilter
- Move FeatureUsage code into MicCheck.Api.Features.Usage namespace
- Convert logic-free data classes to records per CLAUDE.md (WebhookEvent, FeatureStateResult, ProjectPermissionRequirement, AuditLog, Tag, FeatureUsageDaily)
- Extract IAuditService interface, drop virtual-method mock seam on AuditService
- Split Program.cs DI registrations into per-namespace DependencyRegistration classes

## Test plan
- [x] dotnet build (API + tests) clean
- [x] dotnet test MicCheck.Api.Tests.Unit — 646/646 passing
- [x] pre-push hook (full solution build/test + admin build) passed

Co-authored-by: miccheck-ci <ci@miccheck.local>
Reviewed-on: #7

badges/coverage.svg

@@ -123,7 +123,7 @@
 
         <text x="53" y="15" fill="#010101" fill-opacity=".3">Coverage</text>
         <text x="53" y="14" fill="#fff">Coverage</text>
-        <text class="" x="132.5" y="15" fill="#010101" fill-opacity=".3">69.2%</text><text class="" x="132.5" y="14">69.2%</text>
+        <text class="" x="132.5" y="15" fill="#010101" fill-opacity=".3">68.9%</text><text class="" x="132.5" y="14">68.9%</text>
         
         
         

src/api/MicCheck.Api/Audit/AuditLog.cs

@@ -1,6 +1,6 @@
 namespace MicCheck.Api.Audit;
 
-public class AuditLog
+public record AuditLog
 {
     public int Id { get; init; }
     public required string ResourceType { get; init; }

src/api/MicCheck.Api/Audit/AuditLogQueryService.cs

@@ -6,29 +6,25 @@ namespace MicCheck.Api.Audit;
 
 public class AuditLogQueryService(IMicCheckDbContext db)
 {
-    public async Task<PagedResult<AuditLogResponse>> ListByOrganizationAsync(
+    public async Task<PagedResult<AuditLogResponse>> ListByOrganizationAsync(int organizationId, AuditLogFilter filter, CancellationToken ct = default)
-        int organizationId, AuditLogFilter filter, CancellationToken ct = default)
     {
         var query = db.AuditLogs.Where(l => l.OrganizationId == organizationId);
         return await ApplyFilterAndPageAsync(query, filter, ct);
     }
 
-    public async Task<PagedResult<AuditLogResponse>> ListByProjectAsync(
+    public async Task<PagedResult<AuditLogResponse>> ListByProjectAsync(int projectId, AuditLogFilter filter, CancellationToken ct = default)
-        int projectId, AuditLogFilter filter, CancellationToken ct = default)
     {
         var query = db.AuditLogs.Where(l => l.ProjectId == projectId);
         return await ApplyFilterAndPageAsync(query, filter, ct);
     }
 
-    public async Task<PagedResult<AuditLogResponse>> ListByEnvironmentAsync(
+    public async Task<PagedResult<AuditLogResponse>> ListByEnvironmentAsync(int environmentId, AuditLogFilter filter, CancellationToken ct = default)
-        int environmentId, AuditLogFilter filter, CancellationToken ct = default)
     {
         var query = db.AuditLogs.Where(l => l.EnvironmentId == environmentId);
         return await ApplyFilterAndPageAsync(query, filter, ct);
     }
 
-    private async Task<PagedResult<AuditLogResponse>> ApplyFilterAndPageAsync(
+    private async Task<PagedResult<AuditLogResponse>> ApplyFilterAndPageAsync(IQueryable<AuditLog> query, AuditLogFilter filter, CancellationToken ct)
-        IQueryable<AuditLog> query, AuditLogFilter filter, CancellationToken ct)
     {
         if (filter.From.HasValue)
             query = query.Where(l => l.CreatedAt >= filter.From.Value);
@@ -66,4 +62,4 @@ public class AuditLogQueryService(IMicCheckDbContext db)
 
         return new PagedResult<AuditLogResponse>(total, items);
     }
-}
+}

src/api/MicCheck.Api/Audit/AuditService.cs

@@ -4,7 +4,7 @@ using MicCheck.Api.Webhooks;
 
 namespace MicCheck.Api.Audit;
 
-public class AuditService(IMicCheckDbContext db, IHttpContextAccessor httpContextAccessor, WebhookQueue webhookQueue)
+public class AuditService(IMicCheckDbContext db, IHttpContextAccessor httpContextAccessor, WebhookQueue webhookQueue) : IAuditService
 {
     private static readonly JsonSerializerOptions JsonOptions = new()
     {
@@ -12,7 +12,7 @@ public class AuditService(IMicCheckDbContext db, IHttpContextAccessor httpContex
         PropertyNamingPolicy = JsonNamingPolicy.CamelCase
     };
 
-    public virtual async Task RecordAsync(
+    public async Task RecordAsync(
         string resourceType,
         string resourceId,
         string action,
@@ -33,7 +33,7 @@ public class AuditService(IMicCheckDbContext db, IHttpContextAccessor httpContex
             }, JsonOptions);
         }
 
-        var actorUserId = ResolveActorUserId();
+        var actorUserId = GetCurrentUserId();
 
         var log = new AuditLog
         {
@@ -68,7 +68,7 @@ public class AuditService(IMicCheckDbContext db, IHttpContextAccessor httpContex
     }
 
     // Backward-compatible overload used by existing callers
-    public virtual async Task LogAsync(
+    public async Task LogAsync(
         string resourceType,
         string resourceId,
         string action,
@@ -78,7 +78,7 @@ public class AuditService(IMicCheckDbContext db, IHttpContextAccessor httpContex
         string? changes = null,
         CancellationToken ct = default)
     {
-        var actorUserId = ResolveActorUserId();
+        var actorUserId = GetCurrentUserId();
 
         var log = new AuditLog
         {
@@ -112,9 +112,33 @@ public class AuditService(IMicCheckDbContext db, IHttpContextAccessor httpContex
         });
     }
 
-    private int? ResolveActorUserId()
+    private int? GetCurrentUserId()
     {
         var claim = httpContextAccessor.HttpContext?.User.FindFirst(System.Security.Claims.ClaimTypes.NameIdentifier)?.Value;
         return int.TryParse(claim, out var id) ? id : null;
     }
 }
+
+public interface IAuditService
+{
+    Task RecordAsync(
+        string resourceType,
+        string resourceId,
+        string action,
+        int organizationId,
+        int? projectId = null,
+        int? environmentId = null,
+        object? before = null,
+        object? after = null,
+        CancellationToken ct = default);
+
+    Task LogAsync(
+        string resourceType,
+        string resourceId,
+        string action,
+        int organizationId,
+        int? projectId = null,
+        int? environmentId = null,
+        string? changes = null,
+        CancellationToken ct = default);
+}

src/api/MicCheck.Api/Audit/DependencyRegistration.cs

@@ -0,0 +1,12 @@
+namespace MicCheck.Api.Audit;
+
+public static class DependencyRegistration
+{
+    public static IServiceCollection AddAuditServices(this IServiceCollection services)
+    {
+        services.AddScoped<IAuditService, AuditService>();
+        services.AddScoped<AuditLogQueryService>();
+
+        return services;
+    }
+}

src/api/MicCheck.Api/Common/DependencyRegistration.cs

@@ -0,0 +1,65 @@
+using System.Text;
+using MicCheck.Api.Common.Security.ApiKeys;
+using MicCheck.Api.Common.Security.Authentication;
+using MicCheck.Api.Common.Security.Authorization;
+using MicCheck.Api.Common.Validation;
+using Microsoft.AspNetCore.Authentication;
+using Microsoft.AspNetCore.Authentication.JwtBearer;
+using Microsoft.AspNetCore.Authorization;
+using Microsoft.AspNetCore.Mvc;
+using Microsoft.IdentityModel.Tokens;
+
+namespace MicCheck.Api.Common;
+
+public static class DependencyRegistration
+{
+    public static IServiceCollection AddCommonServices(this IServiceCollection services, IConfiguration configuration)
+    {
+        services.AddAuthentication()
+            .AddScheme<AuthenticationSchemeOptions, EnvironmentKeyAuthenticationHandler>(
+                EnvironmentKeyAuthenticationHandler.SchemeName, _ => { })
+            .AddScheme<AuthenticationSchemeOptions, ApiKeyAuthenticationHandler>(
+                ApiKeyAuthenticationHandler.SchemeName, _ => { })
+            .AddJwtBearer(JwtBearerDefaults.AuthenticationScheme, options =>
+            {
+                options.TokenValidationParameters = new TokenValidationParameters
+                {
+                    ValidateIssuer = true,
+                    ValidateAudience = true,
+                    ValidateIssuerSigningKey = true,
+                    ValidIssuer = configuration["Jwt:Issuer"],
+                    ValidAudience = configuration["Jwt:Audience"],
+                    IssuerSigningKey = new SymmetricSecurityKey(
+                        Encoding.UTF8.GetBytes(configuration["Jwt:SecretKey"]!))
+                };
+            });
+
+        services.AddAuthorization(options =>
+        {
+            options.AddPolicy(AuthorizationPolicies.FlagsApiAccess, policy =>
+                policy.AddAuthenticationSchemes(EnvironmentKeyAuthenticationHandler.SchemeName)
+                      .RequireClaim("EnvironmentId"));
+
+            options.AddPolicy(AuthorizationPolicies.AdminApiAccess, policy =>
+                policy.AddAuthenticationSchemes(ApiKeyAuthenticationHandler.SchemeName, JwtBearerDefaults.AuthenticationScheme)
+                      .RequireAuthenticatedUser());
+
+            options.AddPolicy(AuthorizationPolicies.OrganizationAdmin, policy =>
+                policy.AddAuthenticationSchemes(ApiKeyAuthenticationHandler.SchemeName, JwtBearerDefaults.AuthenticationScheme)
+                      .RequireClaim("OrganizationRole", "Admin"));
+        });
+
+        services.AddScoped<ITokenService, TokenService>();
+        services.AddScoped<AuthService>();
+        services.AddScoped<ApiKeyService>();
+        services.AddScoped<IAuthorizationHandler, ProjectPermissionRequirementHandler>();
+
+        services.AddModelValidatorsFromAssemblyContaining<Program>();
+        services.Configure<ApiBehaviorOptions>(options =>
+        {
+            options.InvalidModelStateResponseFactory = context => ValidationProblemResponseFactory.Create(context.ModelState);
+        });
+
+        return services;
+    }
+}

src/api/MicCheck.Api/Common/Guard.cs

@@ -0,0 +1,40 @@
+namespace MicCheck.Api.Common;
+
+public static class Guard
+{
+    public static void Null<T>(T t, string parameterName) where T : class
+    {
+        if (t is null)
+            throw new ArgumentNullException(parameterName, $"{nameof(parameterName)} can not be null");
+    }
+
+    public static void Empty(string value, string parameterName)
+    {
+        if (string.IsNullOrWhiteSpace(value))
+            throw new ArgumentException($"{parameterName} can not be empty", parameterName);
+    }
+
+    public static void Empty<T>(IEnumerable<T> collection, string parameterName)
+    {
+        if (collection == null || !collection.Any())
+            throw new ArgumentException($"{parameterName} can not be empty", parameterName);
+    }
+
+    public static void Negative(int value, string parameterName)
+    {
+        if (value < 0)
+            throw new ArgumentOutOfRangeException(parameterName, $"{parameterName} must be a positive number or zero");
+    }
+
+    public static void NegativeOrZero(int value, string parameterName)
+    {
+        if (value <= 0)
+            throw new ArgumentOutOfRangeException(parameterName, $"{nameof(parameterName)} must be a positive number greater then zero");
+    }
+
+    public static void Default<T>(T value, string parameterName)
+    {
+        if (EqualityComparer<T>.Default.Equals(value, default))
+            throw new ArgumentException($"{parameterName} can not be a default value", parameterName);
+    }
+}

src/api/MicCheck.Api/Common/Security/Authorization/ProjectPermissionRequirement.cs

@@ -2,9 +2,4 @@ using Microsoft.AspNetCore.Authorization;
 
 namespace MicCheck.Api.Common.Security.Authorization;
 
-public class ProjectPermissionRequirement : IAuthorizationRequirement
+public record ProjectPermissionRequirement(ProjectPermission Permission) : IAuthorizationRequirement;
-{
-    public ProjectPermission Permission { get; }
-
-    public ProjectPermissionRequirement(ProjectPermission permission) => Permission = permission;
-}

src/api/MicCheck.Api/Common/Validation/IModelValidator.cs

@@ -0,0 +1,13 @@
+namespace MicCheck.Api.Common.Validation;
+
+public interface IModelValidator
+{
+    ValidationResult Validate(object model);
+}
+
+public interface IModelValidator<in T> : IModelValidator
+{
+    ValidationResult Validate(T model);
+
+    ValidationResult IModelValidator.Validate(object model) => Validate((T)model);
+}

src/api/MicCheck.Api/Common/Validation/ModelValidationActionFilter.cs

@@ -0,0 +1,28 @@
+using Microsoft.AspNetCore.Mvc.Filters;
+
+namespace MicCheck.Api.Common.Validation;
+
+public class ModelValidationActionFilter : IActionFilter
+{
+    public void OnActionExecuting(ActionExecutingContext context)
+    {
+        foreach (var argument in context.ActionArguments.Values)
+        {
+            if (argument is null) continue;
+
+            var validatorType = typeof(IModelValidator<>).MakeGenericType(argument.GetType());
+            if (context.HttpContext.RequestServices.GetService(validatorType) is not IModelValidator validator) continue;
+
+            var result = validator.Validate(argument);
+            foreach (var error in result.Errors)
+                context.ModelState.AddModelError(error.PropertyName, error.Message);
+        }
+
+        if (!context.ModelState.IsValid)
+            context.Result = ValidationProblemResponseFactory.Create(context.ModelState);
+    }
+
+    public void OnActionExecuted(ActionExecutedContext context)
+    {
+    }
+}

src/api/MicCheck.Api/Common/Validation/ModelValidatorServiceCollectionExtensions.cs

@@ -0,0 +1,20 @@
+using Microsoft.Extensions.DependencyInjection;
+
+namespace MicCheck.Api.Common.Validation;
+
+public static class ModelValidatorServiceCollectionExtensions
+{
+    public static IServiceCollection AddModelValidatorsFromAssemblyContaining<TMarker>(this IServiceCollection services)
+    {
+        var registrations = typeof(TMarker).Assembly.GetTypes()
+            .Where(type => !type.IsAbstract && !type.IsInterface)
+            .SelectMany(type => type.GetInterfaces()
+                .Where(i => i.IsGenericType && i.GetGenericTypeDefinition() == typeof(IModelValidator<>))
+                .Select(i => (Interface: i, Implementation: type)));
+
+        foreach (var (@interface, implementation) in registrations)
+            services.AddScoped(@interface, implementation);
+
+        return services;
+    }
+}

src/api/MicCheck.Api/Common/Validation/ValidationProblemResponseFactory.cs

@@ -0,0 +1,18 @@
+using Microsoft.AspNetCore.Mvc;
+using Microsoft.AspNetCore.Mvc.ModelBinding;
+
+namespace MicCheck.Api.Common.Validation;
+
+public static class ValidationProblemResponseFactory
+{
+    public static IActionResult Create(ModelStateDictionary modelState)
+    {
+        var errors = modelState
+            .Where(e => e.Value?.Errors.Count > 0)
+            .ToDictionary(
+                kvp => kvp.Key,
+                kvp => kvp.Value!.Errors.Select(e => e.ErrorMessage).ToArray());
+
+        return new UnprocessableEntityObjectResult(new { errors });
+    }
+}

src/api/MicCheck.Api/Common/Validation/ValidationResult.cs

@@ -0,0 +1,14 @@
+namespace MicCheck.Api.Common.Validation;
+
+public record ValidationError(string PropertyName, string Message);
+
+public class ValidationResult
+{
+    private readonly List<ValidationError> _errors = [];
+
+    public IReadOnlyList<ValidationError> Errors => _errors;
+    public bool IsValid => _errors.Count == 0;
+    public bool IsInvalid => _errors.Count > 0;
+
+    public void AddError(string propertyName, string message) => _errors.Add(new ValidationError(propertyName, message));
+}

src/api/MicCheck.Api/Data/Configurations/FeatureUsageDailyConfiguration.cs

@@ -1,4 +1,4 @@
-using MicCheck.Api.Features;
+using MicCheck.Api.Features.Usage;
 using Microsoft.EntityFrameworkCore;
 using Microsoft.EntityFrameworkCore.Metadata.Builders;
 

src/api/MicCheck.Api/Data/DependencyRegistration.cs

@@ -0,0 +1,21 @@
+using Microsoft.EntityFrameworkCore;
+
+namespace MicCheck.Api.Data;
+
+public static class DependencyRegistration
+{
+    public static IServiceCollection AddDataServices(this IServiceCollection services, IConfiguration configuration)
+    {
+        services.AddScoped<DatabaseSeeder>();
+
+        var connectionString = configuration.GetConnectionString("miccheck")
+            ?? (System.Environment.GetEnvironmentVariable("DATABASE_URL") is { } databaseUrl
+                ? DatabaseUrlParser.ToNpgsqlConnectionString(databaseUrl)
+                : configuration.GetConnectionString("DefaultConnection")!);
+
+        services.AddDbContext<MicCheckDbContext>(options => options.UseNpgsql(connectionString));
+        services.AddScoped<IMicCheckDbContext>(sp => sp.GetRequiredService<MicCheckDbContext>());
+
+        return services;
+    }
+}

src/api/MicCheck.Api/Data/MicCheckDbContext.cs

@@ -2,6 +2,7 @@ using MicCheck.Api.Common.Security.ApiKeys;
 using MicCheck.Api.Audit;
 using MicCheck.Api.Common.Security.Authorization;
 using MicCheck.Api.Features;
+using MicCheck.Api.Features.Usage;
 using MicCheck.Api.Identities;
 using MicCheck.Api.Organizations;
 using MicCheck.Api.Projects;

src/api/MicCheck.Api/Environments/CloneEnvironmentRequest.cs

@@ -1,13 +1,20 @@
-using FluentValidation;
+using MicCheck.Api.Common.Validation;
 
 namespace MicCheck.Api.Environments;
 
 public record CloneEnvironmentRequest(string Name);
 
-public class CloneEnvironmentRequestValidator : AbstractValidator<CloneEnvironmentRequest>
+public class CloneEnvironmentRequestValidator : IModelValidator<CloneEnvironmentRequest>
 {
-    public CloneEnvironmentRequestValidator()
+    public ValidationResult Validate(CloneEnvironmentRequest model)
     {
-        RuleFor(x => x.Name).NotEmpty().MaximumLength(200);
+        var result = new ValidationResult();
+
+        if (string.IsNullOrEmpty(model.Name))
+            result.AddError(nameof(model.Name), "'Name' must not be empty.");
+        else if (model.Name.Length > 200)
+            result.AddError(nameof(model.Name), "'Name' must be 200 characters or fewer.");
+
+        return result;
     }
 }

src/api/MicCheck.Api/Environments/CreateEnvironmentRequest.cs

@@ -1,14 +1,23 @@
-using FluentValidation;
+using MicCheck.Api.Common.Validation;
 
 namespace MicCheck.Api.Environments;
 
 public record CreateEnvironmentRequest(string Name, int ProjectId);
 
-public class CreateEnvironmentRequestValidator : AbstractValidator<CreateEnvironmentRequest>
+public class CreateEnvironmentRequestValidator : IModelValidator<CreateEnvironmentRequest>
 {
-    public CreateEnvironmentRequestValidator()
+    public ValidationResult Validate(CreateEnvironmentRequest model)
     {
-        RuleFor(x => x.Name).NotEmpty().MaximumLength(200);
+        var result = new ValidationResult();
-        RuleFor(x => x.ProjectId).GreaterThan(0);
+
+        if (string.IsNullOrEmpty(model.Name))
+            result.AddError(nameof(model.Name), "'Name' must not be empty.");
+        else if (model.Name.Length > 200)
+            result.AddError(nameof(model.Name), "'Name' must be 200 characters or fewer.");
+
+        if (model.ProjectId <= 0)
+            result.AddError(nameof(model.ProjectId), "'Project Id' must be greater than 0.");
+
+        return result;
     }
 }

src/api/MicCheck.Api/Environments/DependencyRegistration.cs

@@ -0,0 +1,12 @@
+namespace MicCheck.Api.Environments;
+
+public static class DependencyRegistration
+{
+    public static IServiceCollection AddEnvironmentsServices(this IServiceCollection services)
+    {
+        services.AddScoped<EnvironmentService>();
+        services.AddScoped<EnvironmentDocumentService>();
+
+        return services;
+    }
+}

src/api/MicCheck.Api/Environments/EnvironmentService.cs

@@ -7,7 +7,7 @@ using AppEnvironment = MicCheck.Api.Environments.Environment;
 
 namespace MicCheck.Api.Environments;
 
-public class EnvironmentService(IMicCheckDbContext db, AuditService auditService)
+public class EnvironmentService(IMicCheckDbContext db, IAuditService auditService)
 {
     public async Task<IReadOnlyList<AppEnvironment>> ListByProjectAsync(int projectId, CancellationToken ct = default)
     {

src/api/MicCheck.Api/Environments/UpdateEnvironmentRequest.cs

@@ -1,13 +1,20 @@
-using FluentValidation;
+using MicCheck.Api.Common.Validation;
 
 namespace MicCheck.Api.Environments;
 
 public record UpdateEnvironmentRequest(string Name);
 
-public class UpdateEnvironmentRequestValidator : AbstractValidator<UpdateEnvironmentRequest>
+public class UpdateEnvironmentRequestValidator : IModelValidator<UpdateEnvironmentRequest>
 {
-    public UpdateEnvironmentRequestValidator()
+    public ValidationResult Validate(UpdateEnvironmentRequest model)
     {
-        RuleFor(x => x.Name).NotEmpty().MaximumLength(200);
+        var result = new ValidationResult();
+
+        if (string.IsNullOrEmpty(model.Name))
+            result.AddError(nameof(model.Name), "'Name' must not be empty.");
+        else if (model.Name.Length > 200)
+            result.AddError(nameof(model.Name), "'Name' must be 200 characters or fewer.");
+
+        return result;
     }
 }

src/api/MicCheck.Api/Features/CreateFeatureRequest.cs

@@ -1,26 +1,28 @@
-using FluentValidation;
+using System.Text.RegularExpressions;
+using MicCheck.Api.Common.Validation;
 
 namespace MicCheck.Api.Features;
 
-public record CreateFeatureRequest(
+public record CreateFeatureRequest(string Name, FeatureType Type, string? InitialValue, string? Description);
-    string Name,
-    FeatureType Type,
-    string? InitialValue,
-    string? Description
-);
 
-public class CreateFeatureRequestValidator : AbstractValidator<CreateFeatureRequest>
+public class CreateFeatureRequestValidator : IModelValidator<CreateFeatureRequest>
 {
-    public CreateFeatureRequestValidator()
+    private static readonly Regex NamePattern = new("^[a-zA-Z0-9_-]+$");
-    {
-        RuleFor(x => x.Name)
-            .NotEmpty()
-            .MaximumLength(150)
-            .Matches("^[a-zA-Z0-9_-]+$")
-            .WithMessage("Name may only contain letters, digits, underscores, and hyphens.");
 
-        RuleFor(x => x.InitialValue)
+    public ValidationResult Validate(CreateFeatureRequest model)
-            .MaximumLength(20_000)
+    {
-            .When(x => x.InitialValue is not null);
+        var result = new ValidationResult();
+
+        if (string.IsNullOrEmpty(model.Name))
+            result.AddError(nameof(model.Name), "'Name' must not be empty.");
+        else if (model.Name.Length > 150)
+            result.AddError(nameof(model.Name), "'Name' must be 150 characters or fewer.");
+        else if (!NamePattern.IsMatch(model.Name))
+            result.AddError(nameof(model.Name), "Name may only contain letters, digits, underscores, and hyphens.");
+
+        if (model.InitialValue is not null && model.InitialValue.Length > 20_000)
+            result.AddError(nameof(model.InitialValue), "'Initial Value' must be 20000 characters or fewer.");
+
+        return result;
     }
 }

src/api/MicCheck.Api/Features/CreateTagRequest.cs

@@ -1,16 +1,30 @@
-using FluentValidation;
+using System.Text.RegularExpressions;
+using MicCheck.Api.Common.Validation;
 
 namespace MicCheck.Api.Features;
 
 public record CreateTagRequest(string Label, string Color);
 
-public class CreateTagRequestValidator : AbstractValidator<CreateTagRequest>
+public class CreateTagRequestValidator : IModelValidator<CreateTagRequest>
 {
-    public CreateTagRequestValidator()
+    private static readonly Regex ColorPattern = new("^#[0-9A-Fa-f]{3,6}$");
+
+    public ValidationResult Validate(CreateTagRequest model)
     {
-        RuleFor(x => x.Label).NotEmpty().MaximumLength(100);
+        var result = new ValidationResult();
-        RuleFor(x => x.Color).NotEmpty().MaximumLength(20)
+
-            .Matches("^#[0-9A-Fa-f]{3,6}$")
+        if (string.IsNullOrEmpty(model.Label))
-            .WithMessage("Color must be a valid hex color (e.g. #FF0000).");
+            result.AddError(nameof(model.Label), "'Label' must not be empty.");
+        else if (model.Label.Length > 100)
+            result.AddError(nameof(model.Label), "'Label' must be 100 characters or fewer.");
+
+        if (string.IsNullOrEmpty(model.Color))
+            result.AddError(nameof(model.Color), "'Color' must not be empty.");
+        else if (model.Color.Length > 20)
+            result.AddError(nameof(model.Color), "'Color' must be 20 characters or fewer.");
+        else if (!ColorPattern.IsMatch(model.Color))
+            result.AddError(nameof(model.Color), "Color must be a valid hex color (e.g. #FF0000).");
+
+        return result;
     }
 }

src/api/MicCheck.Api/Features/DependencyRegistration.cs

@@ -0,0 +1,20 @@
+using MicCheck.Api.Features.Usage;
+
+namespace MicCheck.Api.Features;
+
+public static class DependencyRegistration
+{
+    public static IServiceCollection AddFeaturesServices(this IServiceCollection services)
+    {
+        services.AddScoped<FeatureEvaluationService>();
+        services.AddSingleton<FlagCache>();
+        services.AddScoped<FeatureService>();
+        services.AddScoped<FeatureStateService>();
+        services.AddScoped<FeatureSegmentService>();
+        services.AddScoped<TagService>();
+
+        services.AddFeatureUsageServices();
+
+        return services;
+    }
+}

src/api/MicCheck.Api/Features/FeatureEvaluationService.cs

@@ -1,4 +1,5 @@
 using MicCheck.Api.Data;
+using MicCheck.Api.Features.Usage;
 using MicCheck.Api.Identities;
 using MicCheck.Api.Segments;
 using Microsoft.EntityFrameworkCore;

src/api/MicCheck.Api/Features/FeatureService.cs

@@ -6,7 +6,7 @@ using Microsoft.EntityFrameworkCore;
 
 namespace MicCheck.Api.Features;
 
-public class FeatureService(IMicCheckDbContext db, AuditService auditService, WebhookQueue webhookQueue)
+public class FeatureService(IMicCheckDbContext db, IAuditService auditService, WebhookQueue webhookQueue)
 {
     private const int MaxFeaturesPerProject = 400;
 
@@ -23,13 +23,7 @@ public class FeatureService(IMicCheckDbContext db, AuditService auditService, We
         return await db.Features.Include(f => f.Tags).FirstOrDefaultAsync(f => f.Id == id, ct);
     }
 
-    public async Task<Feature> CreateAsync(
+    public async Task<Feature> CreateAsync(int projectId, string name, FeatureType type, string? initialValue, string? description, CancellationToken ct = default)
-        int projectId,
-        string name,
-        FeatureType type,
-        string? initialValue,
-        string? description,
-        CancellationToken ct = default)
     {
         var count = await db.Features.CountAsync(f => f.ProjectId == projectId, ct);
         if (count >= MaxFeaturesPerProject)
@@ -78,8 +72,7 @@ public class FeatureService(IMicCheckDbContext db, AuditService auditService, We
         return feature;
     }
 
-    public async Task<Feature> UpdateAsync(
+    public async Task<Feature> UpdateAsync(int id, string name, string? description, CancellationToken ct = default)
-        int id, string name, string? description, CancellationToken ct = default)
     {
         var feature = await db.Features.Include(f => f.Tags).FirstOrDefaultAsync(f => f.Id == id, ct)
             ?? throw new KeyNotFoundException($"Feature {id} not found.");
@@ -162,11 +155,7 @@ public class FeatureService(IMicCheckDbContext db, AuditService auditService, We
                     EventType = WebhookEventTypes.FlagDeleted,
                     EnvironmentId = env.Id,
                     OrganizationId = project.OrganizationId,
-                    Data = new FlagDeletedData(
+                    Data = new FlagDeletedData(null, DateTimeOffset.UtcNow, new FeatureSummary(feature.Id, feature.Name)) });
-                        null,
-                        DateTimeOffset.UtcNow,
-                        new FeatureSummary(feature.Id, feature.Name))
-                });
             }
         }
     }

src/api/MicCheck.Api/Features/FeatureStateResult.cs

@@ -1,6 +1,6 @@
 namespace MicCheck.Api.Features;
 
-public class FeatureStateResult
+public record FeatureStateResult
 {
     public required Feature Feature { get; init; }
     public bool Enabled { get; init; }

src/api/MicCheck.Api/Features/FeatureStateService.cs

@@ -5,7 +5,7 @@ using Microsoft.EntityFrameworkCore;
 
 namespace MicCheck.Api.Features;
 
-public class FeatureStateService(IMicCheckDbContext db, WebhookQueue webhookQueue, AuditService auditService)
+public class FeatureStateService(IMicCheckDbContext db, WebhookQueue webhookQueue, IAuditService auditService)
 {
     public async Task<IReadOnlyList<FeatureState>> ListByEnvironmentAsync(int environmentId, CancellationToken ct = default)
     {

src/api/MicCheck.Api/Features/FeatureUsageDaily.cs

@@ -1,12 +0,0 @@
-namespace MicCheck.Api.Features;
-
-public class FeatureUsageDaily
-{
-    public int Id { get; init; }
-    public int EnvironmentId { get; init; }
-    public int FeatureId { get; init; }
-    public required string FeatureName { get; set; }
-    public DateOnly UsageDate { get; init; }
-    public long Count { get; set; }
-    public DateTimeOffset UpdatedAt { get; set; }
-}

src/api/MicCheck.Api/Features/FlagCache.cs

@@ -12,11 +12,9 @@ public class FlagCache(IMemoryCache cache)
         return flags;
     }
 
-    public void Set(int environmentId, IReadOnlyList<FeatureStateResult> flags)
+    public void Set(int environmentId, IReadOnlyList<FeatureStateResult> flags) => cache.Set(CacheKey(environmentId), flags, CacheDuration);
-        => cache.Set(CacheKey(environmentId), flags, CacheDuration);
 
-    public void Invalidate(int environmentId)
+    public void Invalidate(int environmentId) => cache.Remove(CacheKey(environmentId));
-        => cache.Remove(CacheKey(environmentId));
 
     private static string CacheKey(int environmentId) => $"flags:{environmentId}";
 }

src/api/MicCheck.Api/Features/Tag.cs

@@ -1,9 +1,9 @@
 namespace MicCheck.Api.Features;
 
-public class Tag
+public record Tag
 {
     public int Id { get; init; }
-    public required string Label { get; set; }
+    public required string Label { get; init; }
-    public required string Color { get; set; }
+    public required string Color { get; init; }
     public int ProjectId { get; init; }
 }

src/api/MicCheck.Api/Features/TagsController.cs

@@ -8,23 +8,24 @@ namespace MicCheck.Api.Features;
 [ApiController]
 [Authorize(Policy = AuthorizationPolicies.AdminApiAccess)]
 [EnableRateLimiting("AdminApi")]
+[Route("api/v1/project/{projectId}")]
 public class TagsController(TagService tagService) : ControllerBase
 {
-    [HttpGet("api/v1/project/{projectId}/tags")]
+    [HttpGet("tags")]
     public async Task<ActionResult<IReadOnlyList<TagResponse>>> List(int projectId, CancellationToken ct)
     {
         var tags = await tagService.ListByProjectAsync(projectId, ct);
         return Ok(tags.Select(TagResponse.From).ToList());
     }
 
-    [HttpPost("api/v1/project/{projectId}/tags")]
+    [HttpPost("tags")]
     public async Task<ActionResult<TagResponse>> Create(int projectId, CreateTagRequest request, CancellationToken ct)
     {
         var tag = await tagService.CreateAsync(projectId, request.Label, request.Color, ct);
         return CreatedAtAction(nameof(List), new { projectId }, TagResponse.From(tag));
     }
 
-    [HttpDelete("api/v1/project/{projectId}/tag/{id}")]
+    [HttpDelete("tag/{id}")]
     public async Task<IActionResult> Delete(int projectId, int id, CancellationToken ct)
     {
         var tag = await tagService.FindByIdAsync(id, ct);

src/api/MicCheck.Api/Features/UpdateFeatureRequest.cs

@@ -1,20 +1,25 @@
-using FluentValidation;
+using System.Text.RegularExpressions;
+using MicCheck.Api.Common.Validation;
 
 namespace MicCheck.Api.Features;
 
-public record UpdateFeatureRequest(
+public record UpdateFeatureRequest(string Name, string? Description);
-    string Name,
-    string? Description
-);
 
-public class UpdateFeatureRequestValidator : AbstractValidator<UpdateFeatureRequest>
+public class UpdateFeatureRequestValidator : IModelValidator<UpdateFeatureRequest>
 {
-    public UpdateFeatureRequestValidator()
+    private static readonly Regex NamePattern = new("^[a-zA-Z0-9_-]+$");
+
+    public ValidationResult Validate(UpdateFeatureRequest model)
     {
-        RuleFor(x => x.Name)
+        var result = new ValidationResult();
-            .NotEmpty()
+
-            .MaximumLength(150)
+        if (string.IsNullOrEmpty(model.Name))
-            .Matches("^[a-zA-Z0-9_-]+$")
+            result.AddError(nameof(model.Name), "'Name' must not be empty.");
-            .WithMessage("Name may only contain letters, digits, underscores, and hyphens.");
+        else if (model.Name.Length > 150)
+            result.AddError(nameof(model.Name), "'Name' must be 150 characters or fewer.");
+        else if (!NamePattern.IsMatch(model.Name))
+            result.AddError(nameof(model.Name), "Name may only contain letters, digits, underscores, and hyphens.");
+
+        return result;
     }
 }

src/api/MicCheck.Api/Features/Usage/DependencyRegistration.cs

@@ -0,0 +1,13 @@
+namespace MicCheck.Api.Features.Usage;
+
+public static class DependencyRegistration
+{
+    public static IServiceCollection AddFeatureUsageServices(this IServiceCollection services)
+    {
+        services.AddSingleton<FeatureUsageMetrics>();
+        services.AddScoped<FeatureUsageQueryService>();
+        services.AddHostedService<FeatureUsageFlushBackgroundService>();
+
+        return services;
+    }
+}

src/api/MicCheck.Api/Features/Usage/FeatureUsageBucketKey.cs

@@ -1,3 +1,3 @@
-namespace MicCheck.Api.Features;
+namespace MicCheck.Api.Features.Usage;
 
 public record struct FeatureUsageBucketKey(int EnvironmentId, int FeatureId, string FeatureName, DateOnly UsageDate);

src/api/MicCheck.Api/Features/Usage/FeatureUsageController.cs

@@ -4,7 +4,7 @@ using Microsoft.AspNetCore.Mvc;
 using Microsoft.AspNetCore.RateLimiting;
 using Microsoft.Extensions.Caching.Memory;
 
-namespace MicCheck.Api.Features;
+namespace MicCheck.Api.Features.Usage;
 
 [ApiController]
 [Route("api/v1/environment/{environmentId}/usage")]

src/api/MicCheck.Api/Features/Usage/FeatureUsageDaily.cs

@@ -0,0 +1,12 @@
+namespace MicCheck.Api.Features.Usage;
+
+public record FeatureUsageDaily
+{
+    public int Id { get; init; }
+    public int EnvironmentId { get; init; }
+    public int FeatureId { get; init; }
+    public required string FeatureName { get; init; }
+    public DateOnly UsageDate { get; init; }
+    public long Count { get; init; }
+    public DateTimeOffset UpdatedAt { get; init; }
+}

src/api/MicCheck.Api/Features/Usage/FeatureUsageFlushBackgroundService.cs

@@ -2,7 +2,7 @@ using System.Diagnostics.CodeAnalysis;
 using MicCheck.Api.Data;
 using Microsoft.EntityFrameworkCore;
 
-namespace MicCheck.Api.Features;
+namespace MicCheck.Api.Features.Usage;
 
 [ExcludeFromCodeCoverage(Justification = "Timer-driven BackgroundService that issues raw SQL through a DI-scoped concrete MicCheckDbContext; exercising it cleanly requires a live DB, which CLAUDE.md disallows (no WebApplicationFactory/InMemory). DrainAccumulated's bucketing logic is covered by FeatureUsageMetricsTests.")]
 public class FeatureUsageFlushBackgroundService(

src/api/MicCheck.Api/Features/Usage/FeatureUsageMetrics.cs

@@ -1,7 +1,7 @@
 using System.Collections.Concurrent;
 using System.Diagnostics.Metrics;
 
-namespace MicCheck.Api.Features;
+namespace MicCheck.Api.Features.Usage;
 
 public class FeatureUsageMetrics : IDisposable
 {

src/api/MicCheck.Api/Features/Usage/FeatureUsageQueryService.cs

@@ -1,7 +1,7 @@
 using MicCheck.Api.Data;
 using Microsoft.EntityFrameworkCore;
 
-namespace MicCheck.Api.Features;
+namespace MicCheck.Api.Features.Usage;
 
 public class FeatureUsageQueryService(IMicCheckDbContext db)
 {

src/api/MicCheck.Api/Features/Usage/FeatureUsageResponses.cs

@@ -1,9 +1,7 @@
-namespace MicCheck.Api.Features;
+namespace MicCheck.Api.Features.Usage;
 
 public record TopFeatureUsage(int FeatureId, string FeatureName, long Count);
 
 public record DailyUsage(DateOnly Date, long TotalCount, IReadOnlyList<TopFeatureUsage> Features);
 
-public record DashboardUsageResponse(
+public record DashboardUsageResponse(IReadOnlyList<TopFeatureUsage> TopFeaturesLastDay, IReadOnlyList<DailyUsage> DailyUsage);
-    IReadOnlyList<TopFeatureUsage> TopFeaturesLastDay,
-    IReadOnlyList<DailyUsage> DailyUsage);

src/api/MicCheck.Api/Identities/DependencyRegistration.cs

@@ -0,0 +1,12 @@
+namespace MicCheck.Api.Identities;
+
+public static class DependencyRegistration
+{
+    public static IServiceCollection AddIdentitiesServices(this IServiceCollection services)
+    {
+        services.AddScoped<IdentityResolutionService>();
+        services.AddScoped<AdminIdentityService>();
+
+        return services;
+    }
+}

src/api/MicCheck.Api/MicCheck.Api.csproj

@@ -9,7 +9,6 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="FluentValidation.AspNetCore" Version="11.3.0" />
     <PackageReference Include="Microsoft.AspNetCore.Authentication.JwtBearer" Version="10.0.5" />
     <PackageReference Include="Microsoft.AspNetCore.OpenApi" Version="10.0.5" />
     <PackageReference Include="Microsoft.OpenApi" Version="2.9.0" />

src/api/MicCheck.Api/Migrations/20260617194113_AddFeatureUsageDaily.Designer.cs

@@ -305,7 +305,7 @@ namespace MicCheck.Api.Migrations
                     b.ToTable("FeatureStates");
                 });
 
-            modelBuilder.Entity("MicCheck.Api.Features.FeatureUsageDaily", b =>
+            modelBuilder.Entity("MicCheck.Api.Features.Usage.FeatureUsageDaily", b =>
                 {
                     b.Property<int>("Id")
                         .ValueGeneratedOnAdd()

src/api/MicCheck.Api/Migrations/MicCheckDbContextModelSnapshot.cs

@@ -302,7 +302,7 @@ namespace MicCheck.Api.Migrations
                     b.ToTable("FeatureStates");
                 });
 
-            modelBuilder.Entity("MicCheck.Api.Features.FeatureUsageDaily", b =>
+            modelBuilder.Entity("MicCheck.Api.Features.Usage.FeatureUsageDaily", b =>
                 {
                     b.Property<int>("Id")
                         .ValueGeneratedOnAdd()

src/api/MicCheck.Api/Organizations/CreateOrganizationRequest.cs

@@ -1,13 +1,20 @@
-using FluentValidation;
+using MicCheck.Api.Common.Validation;
 
 namespace MicCheck.Api.Organizations;
 
 public record CreateOrganizationRequest(string Name);
 
-public class CreateOrganizationRequestValidator : AbstractValidator<CreateOrganizationRequest>
+public class CreateOrganizationRequestValidator : IModelValidator<CreateOrganizationRequest>
 {
-    public CreateOrganizationRequestValidator()
+    public ValidationResult Validate(CreateOrganizationRequest model)
     {
-        RuleFor(x => x.Name).NotEmpty().MaximumLength(200);
+        var result = new ValidationResult();
+
+        if (string.IsNullOrEmpty(model.Name))
+            result.AddError(nameof(model.Name), "'Name' must not be empty.");
+        else if (model.Name.Length > 200)
+            result.AddError(nameof(model.Name), "'Name' must be 200 characters or fewer.");
+
+        return result;
     }
 }

src/api/MicCheck.Api/Organizations/DependencyRegistration.cs

@@ -0,0 +1,11 @@
+namespace MicCheck.Api.Organizations;
+
+public static class DependencyRegistration
+{
+    public static IServiceCollection AddOrganizationsServices(this IServiceCollection services)
+    {
+        services.AddScoped<OrganizationService>();
+
+        return services;
+    }
+}

src/api/MicCheck.Api/Organizations/InviteUserRequest.cs

@@ -1,15 +1,23 @@
-using FluentValidation;
+using MicCheck.Api.Common.Validation;
 
 namespace MicCheck.Api.Organizations;
 
 public record InviteUserRequest(int UserId, string Role);
 
-public class InviteUserRequestValidator : AbstractValidator<InviteUserRequest>
+public class InviteUserRequestValidator : IModelValidator<InviteUserRequest>
 {
-    public InviteUserRequestValidator()
+    public ValidationResult Validate(InviteUserRequest model)
     {
-        RuleFor(x => x.UserId).GreaterThan(0);
+        var result = new ValidationResult();
-        RuleFor(x => x.Role).NotEmpty().Must(r => Enum.TryParse<OrganizationRole>(r, true, out _))
+
-            .WithMessage("Role must be 'User' or 'Admin'.");
+        if (model.UserId <= 0)
+            result.AddError(nameof(model.UserId), "'User Id' must be greater than 0.");
+
+        if (string.IsNullOrEmpty(model.Role))
+            result.AddError(nameof(model.Role), "'Role' must not be empty.");
+        else if (!Enum.TryParse<OrganizationRole>(model.Role, true, out _))
+            result.AddError(nameof(model.Role), "Role must be 'User' or 'Admin'.");
+
+        return result;
     }
 }

src/api/MicCheck.Api/Organizations/OrganizationService.cs

@@ -5,7 +5,7 @@ using Microsoft.EntityFrameworkCore;
 
 namespace MicCheck.Api.Organizations;
 
-public class OrganizationService(IMicCheckDbContext db, AuditService auditService)
+public class OrganizationService(IMicCheckDbContext db, IAuditService auditService)
 {
     public async Task<IReadOnlyList<(Organization Org, bool IsPrimary)>> ListForUserAsync(int userId, CancellationToken ct = default)
     {

src/api/MicCheck.Api/Organizations/UpdateOrganizationRequest.cs

@@ -1,13 +1,20 @@
-using FluentValidation;
+using MicCheck.Api.Common.Validation;
 
 namespace MicCheck.Api.Organizations;
 
 public record UpdateOrganizationRequest(string Name);
 
-public class UpdateOrganizationRequestValidator : AbstractValidator<UpdateOrganizationRequest>
+public class UpdateOrganizationRequestValidator : IModelValidator<UpdateOrganizationRequest>
 {
-    public UpdateOrganizationRequestValidator()
+    public ValidationResult Validate(UpdateOrganizationRequest model)
     {
-        RuleFor(x => x.Name).NotEmpty().MaximumLength(200);
+        var result = new ValidationResult();
+
+        if (string.IsNullOrEmpty(model.Name))
+            result.AddError(nameof(model.Name), "'Name' must not be empty.");
+        else if (model.Name.Length > 200)
+            result.AddError(nameof(model.Name), "'Name' must be 200 characters or fewer.");
+
+        return result;
     }
 }

src/api/MicCheck.Api/Program.cs

@@ -1,11 +1,9 @@
-using System.Text;
 using System.Threading.RateLimiting;
-using FluentValidation;
-using FluentValidation.AspNetCore;
-using MicCheck.Api.Common.Security.ApiKeys;
 using MicCheck.Api.Audit;
-using MicCheck.Api.Common.Security.Authentication;
+using MicCheck.Api.Common;
+using MicCheck.Api.Common.Security.ApiKeys;
 using MicCheck.Api.Common.Security.Authorization;
+using MicCheck.Api.Common.Validation;
 using MicCheck.Api.Data;
 using MicCheck.Api.Environments;
 using MicCheck.Api.Features;
@@ -15,14 +13,7 @@ using MicCheck.Api.Projects;
 using MicCheck.Api.Segments;
 using MicCheck.Api.Users;
 using MicCheck.Api.Webhooks;
-using Microsoft.AspNetCore.Authentication;
-using Microsoft.AspNetCore.Authentication.JwtBearer;
-using Microsoft.AspNetCore.Authorization;
-using Microsoft.AspNetCore.Identity;
-using Microsoft.AspNetCore.Mvc;
 using Microsoft.AspNetCore.RateLimiting;
-using Microsoft.EntityFrameworkCore;
-using Microsoft.IdentityModel.Tokens;
 using Scalar.AspNetCore;
 using Serilog;
 
@@ -42,44 +33,12 @@ try
               .WriteTo.Console());
 
     builder.Services.AddOpenApi();
-    builder.Services.AddControllers()
+    builder.Services.AddControllers(options => options.Filters.Add<ModelValidationActionFilter>())
         .AddJsonOptions(options =>
             options.JsonSerializerOptions.Converters.Add(
                 new System.Text.Json.Serialization.JsonStringEnumConverter()));
 
-    builder.Services.AddAuthentication()
+    builder.Services.AddCommonServices(builder.Configuration);
-        .AddScheme<AuthenticationSchemeOptions, EnvironmentKeyAuthenticationHandler>(
-            EnvironmentKeyAuthenticationHandler.SchemeName, _ => { })
-        .AddScheme<AuthenticationSchemeOptions, ApiKeyAuthenticationHandler>(
-            ApiKeyAuthenticationHandler.SchemeName, _ => { })
-        .AddJwtBearer(JwtBearerDefaults.AuthenticationScheme, options =>
-        {
-            options.TokenValidationParameters = new TokenValidationParameters
-            {
-                ValidateIssuer = true,
-                ValidateAudience = true,
-                ValidateIssuerSigningKey = true,
-                ValidIssuer = builder.Configuration["Jwt:Issuer"],
-                ValidAudience = builder.Configuration["Jwt:Audience"],
-                IssuerSigningKey = new SymmetricSecurityKey(
-                    Encoding.UTF8.GetBytes(builder.Configuration["Jwt:SecretKey"]!))
-            };
-        });
-
-    builder.Services.AddAuthorization(options =>
-    {
-        options.AddPolicy(AuthorizationPolicies.FlagsApiAccess, policy =>
-            policy.AddAuthenticationSchemes(EnvironmentKeyAuthenticationHandler.SchemeName)
-                  .RequireClaim("EnvironmentId"));
-
-        options.AddPolicy(AuthorizationPolicies.AdminApiAccess, policy =>
-            policy.AddAuthenticationSchemes(ApiKeyAuthenticationHandler.SchemeName, JwtBearerDefaults.AuthenticationScheme)
-                  .RequireAuthenticatedUser());
-
-        options.AddPolicy(AuthorizationPolicies.OrganizationAdmin, policy =>
-            policy.AddAuthenticationSchemes(ApiKeyAuthenticationHandler.SchemeName, JwtBearerDefaults.AuthenticationScheme)
-                  .RequireClaim("OrganizationRole", "Admin"));
-    });
 
     builder.Services.AddHttpContextAccessor();
 
@@ -92,67 +51,20 @@ try
             limiter.QueueLimit = 0;
         }));
 
-    builder.Services.AddFluentValidationAutoValidation();
-    builder.Services.AddValidatorsFromAssemblyContaining<Program>();
-
-    builder.Services.Configure<ApiBehaviorOptions>(options =>
-    {
-        options.InvalidModelStateResponseFactory = context =>
-        {
-            var errors = context.ModelState
-                .Where(e => e.Value?.Errors.Count > 0)
-                .ToDictionary(
-                    kvp => kvp.Key,
-                    kvp => kvp.Value!.Errors.Select(e => e.ErrorMessage).ToArray());
-            return new UnprocessableEntityObjectResult(new { errors });
-        };
-    });
-
     builder.Services.AddMemoryCache();
     builder.Services.AddMetrics();
 
-    builder.Services.AddScoped<ITokenService, TokenService>();
+    builder.Services.AddAuditServices();
-    builder.Services.AddScoped<AuthService>();
+    builder.Services.AddIdentitiesServices();
-    builder.Services.AddScoped<ApiKeyService>();
+    builder.Services.AddEnvironmentsServices();
-    builder.Services.AddScoped<DatabaseSeeder>();
+    builder.Services.AddSegmentsServices();
-    builder.Services.AddScoped<IPasswordHasher<User>, PasswordHasher<User>>();
+    builder.Services.AddOrganizationsServices();
-    builder.Services.AddScoped<IAuthorizationHandler, ProjectPermissionRequirementHandler>();
+    builder.Services.AddProjectsServices();
-    builder.Services.AddScoped<FeatureEvaluationService>();
+    builder.Services.AddFeaturesServices();
-    builder.Services.AddScoped<IdentityResolutionService>();
+    builder.Services.AddUsersServices();
-    builder.Services.AddScoped<EnvironmentDocumentService>();
+    builder.Services.AddWebhooksServices();
-    builder.Services.AddSingleton<SegmentEvaluator>();
-    builder.Services.AddSingleton<FlagCache>();
-    builder.Services.AddScoped<AuditService>();
-    builder.Services.AddScoped<AuditLogQueryService>();
-    builder.Services.AddScoped<OrganizationService>();
-    builder.Services.AddScoped<ProjectService>();
-    builder.Services.AddScoped<EnvironmentService>();
-    builder.Services.AddScoped<FeatureService>();
-    builder.Services.AddScoped<FeatureStateService>();
-    builder.Services.AddScoped<FeatureSegmentService>();
-    builder.Services.AddScoped<SegmentService>();
-    builder.Services.AddScoped<TagService>();
-    builder.Services.AddScoped<WebhookService>();
-    builder.Services.AddScoped<WebhookDispatcher>();
-    builder.Services.AddScoped<AdminIdentityService>();
-    builder.Services.AddScoped<UserService>();
-    builder.Services.AddSingleton<WebhookQueue>();
-    builder.Services.AddHostedService<WebhookBackgroundService>();
-    builder.Services.AddHostedService<WebhookRetryBackgroundService>();
-    builder.Services.AddSingleton<FeatureUsageMetrics>();
-    builder.Services.AddScoped<FeatureUsageQueryService>();
-    builder.Services.AddHostedService<FeatureUsageFlushBackgroundService>();
-    builder.Services.AddHttpClient("Webhooks", client =>
-        client.DefaultRequestHeaders.Add("User-Agent", "MicCheck-Webhook/1.0"));
 
-    var connectionString = builder.Configuration.GetConnectionString("miccheck")
+    builder.Services.AddDataServices(builder.Configuration);
-        ?? (System.Environment.GetEnvironmentVariable("DATABASE_URL") is { } databaseUrl
-            ? DatabaseUrlParser.ToNpgsqlConnectionString(databaseUrl)
-            : builder.Configuration.GetConnectionString("DefaultConnection")!);
-
-    builder.Services.AddDbContext<MicCheckDbContext>(options =>
-        options.UseNpgsql(connectionString));
-    builder.Services.AddScoped<IMicCheckDbContext>(sp => sp.GetRequiredService<MicCheckDbContext>());
 
     var app = builder.Build();
 

src/api/MicCheck.Api/Projects/CreateProjectRequest.cs

@@ -1,14 +1,23 @@
-using FluentValidation;
+using MicCheck.Api.Common.Validation;
 
 namespace MicCheck.Api.Projects;
 
 public record CreateProjectRequest(string Name, int OrganizationId);
 
-public class CreateProjectRequestValidator : AbstractValidator<CreateProjectRequest>
+public class CreateProjectRequestValidator : IModelValidator<CreateProjectRequest>
 {
-    public CreateProjectRequestValidator()
+    public ValidationResult Validate(CreateProjectRequest model)
     {
-        RuleFor(x => x.Name).NotEmpty().MaximumLength(200);
+        var result = new ValidationResult();
-        RuleFor(x => x.OrganizationId).GreaterThan(0);
+
+        if (string.IsNullOrEmpty(model.Name))
+            result.AddError(nameof(model.Name), "'Name' must not be empty.");
+        else if (model.Name.Length > 200)
+            result.AddError(nameof(model.Name), "'Name' must be 200 characters or fewer.");
+
+        if (model.OrganizationId <= 0)
+            result.AddError(nameof(model.OrganizationId), "'Organization Id' must be greater than 0.");
+
+        return result;
     }
 }

src/api/MicCheck.Api/Projects/DependencyRegistration.cs

@@ -0,0 +1,11 @@
+namespace MicCheck.Api.Projects;
+
+public static class DependencyRegistration
+{
+    public static IServiceCollection AddProjectsServices(this IServiceCollection services)
+    {
+        services.AddScoped<ProjectService>();
+
+        return services;
+    }
+}

src/api/MicCheck.Api/Projects/ProjectService.cs

@@ -5,7 +5,7 @@ using Microsoft.EntityFrameworkCore;
 
 namespace MicCheck.Api.Projects;
 
-public class ProjectService(IMicCheckDbContext db, AuditService auditService)
+public class ProjectService(IMicCheckDbContext db, IAuditService auditService)
 {
     public async Task<IReadOnlyList<Project>> ListByOrganizationAsync(int organizationId, CancellationToken ct = default)
     {

src/api/MicCheck.Api/Projects/SetUserPermissionsRequest.cs

@@ -1,17 +1,25 @@
-using FluentValidation;
+using MicCheck.Api.Common.Security.Authorization;
-using MicCheck.Api.Common.Security.Authorization;
+using MicCheck.Api.Common.Validation;
-
+
-namespace MicCheck.Api.Projects;
+namespace MicCheck.Api.Projects;
-
+
-public record SetUserPermissionsRequest(int UserId, bool IsAdmin, List<string> Permissions);
+public record SetUserPermissionsRequest(int UserId, bool IsAdmin, List<string> Permissions);
-
+
-public class SetUserPermissionsRequestValidator : AbstractValidator<SetUserPermissionsRequest>
+public class SetUserPermissionsRequestValidator : IModelValidator<SetUserPermissionsRequest>
-{
+{
-    public SetUserPermissionsRequestValidator()
+    public ValidationResult Validate(SetUserPermissionsRequest model)
-    {
+    {
-        RuleFor(x => x.UserId).GreaterThan(0);
+        var result = new ValidationResult();
-        RuleForEach(x => x.Permissions)
+
-            .Must(p => Enum.TryParse<ProjectPermission>(p, true, out _))
+        if (model.UserId <= 0)
-            .WithMessage("Invalid permission value.");
+            result.AddError(nameof(model.UserId), "'User Id' must be greater than 0.");
-    }
+
-}
+        foreach (var permission in model.Permissions)
+        {
+            if (!Enum.TryParse<ProjectPermission>(permission, true, out _))
+                result.AddError(nameof(model.Permissions), "Invalid permission value.");
+        }
+
+        return result;
+    }
+}

src/api/MicCheck.Api/Projects/UpdateProjectRequest.cs

@@ -1,13 +1,20 @@
-using FluentValidation;
+using MicCheck.Api.Common.Validation;
 
 namespace MicCheck.Api.Projects;
 
 public record UpdateProjectRequest(string Name, bool HideDisabledFlags);
 
-public class UpdateProjectRequestValidator : AbstractValidator<UpdateProjectRequest>
+public class UpdateProjectRequestValidator : IModelValidator<UpdateProjectRequest>
 {
-    public UpdateProjectRequestValidator()
+    public ValidationResult Validate(UpdateProjectRequest model)
     {
-        RuleFor(x => x.Name).NotEmpty().MaximumLength(200);
+        var result = new ValidationResult();
+
+        if (string.IsNullOrEmpty(model.Name))
+            result.AddError(nameof(model.Name), "'Name' must not be empty.");
+        else if (model.Name.Length > 200)
+            result.AddError(nameof(model.Name), "'Name' must be 200 characters or fewer.");
+
+        return result;
     }
 }

src/api/MicCheck.Api/Segments/CreateSegmentRequest.cs

@@ -1,4 +1,4 @@
-using FluentValidation;
+using MicCheck.Api.Common.Validation;
 
 namespace MicCheck.Api.Segments;
 
@@ -16,24 +16,38 @@ public record CreateSegmentRequest(
     string Name,
     IReadOnlyList<CreateSegmentRuleRequest> Rules);
 
-public class CreateSegmentRequestValidator : AbstractValidator<CreateSegmentRequest>
+public class CreateSegmentRequestValidator : IModelValidator<CreateSegmentRequest>
 {
-    public CreateSegmentRequestValidator()
+    public ValidationResult Validate(CreateSegmentRequest model)
     {
-        RuleFor(x => x.Name).NotEmpty().MaximumLength(200);
+        var result = new ValidationResult();
-        RuleFor(x => x.Rules).NotNull();
+
-        RuleForEach(x => x.Rules).ChildRules(rule =>
+        if (string.IsNullOrEmpty(model.Name))
+            result.AddError(nameof(model.Name), "'Name' must not be empty.");
+        else if (model.Name.Length > 200)
+            result.AddError(nameof(model.Name), "'Name' must be 200 characters or fewer.");
+
+        if (model.Rules is null)
         {
-            rule.RuleFor(r => r.Type)
+            result.AddError(nameof(model.Rules), "'Rules' must not be empty.");
-                .Must(t => Enum.TryParse<SegmentRuleType>(t, true, out _))
+            return result;
-                .WithMessage("Rule type must be 'All', 'Any', or 'None'.");
+        }
-            rule.RuleForEach(r => r.Conditions).ChildRules(cond =>
+
+        foreach (var rule in model.Rules)
+        {
+            if (!Enum.TryParse<SegmentRuleType>(rule.Type, true, out _))
+                result.AddError(nameof(model.Rules), "Rule type must be 'All', 'Any', or 'None'.");
+
+            foreach (var condition in rule.Conditions)
             {
-                cond.RuleFor(c => c.Property).NotEmpty();
+                if (string.IsNullOrEmpty(condition.Property))
-                cond.RuleFor(c => c.Operator)
+                    result.AddError(nameof(model.Rules), "'Property' must not be empty.");
-                    .Must(o => Enum.TryParse<SegmentConditionOperator>(o, true, out _))
+
-                    .WithMessage("Invalid operator.");
+                if (!Enum.TryParse<SegmentConditionOperator>(condition.Operator, true, out _))
-            });
+                    result.AddError(nameof(model.Rules), "Invalid operator.");
-        });
+            }
+        }
+
+        return result;
     }
 }

src/api/MicCheck.Api/Segments/DependencyRegistration.cs

@@ -0,0 +1,12 @@
+namespace MicCheck.Api.Segments;
+
+public static class DependencyRegistration
+{
+    public static IServiceCollection AddSegmentsServices(this IServiceCollection services)
+    {
+        services.AddSingleton<SegmentEvaluator>();
+        services.AddScoped<SegmentService>();
+
+        return services;
+    }
+}

src/api/MicCheck.Api/Segments/SegmentService.cs

@@ -9,7 +9,7 @@ public record SegmentConditionDefinition(string Property, SegmentConditionOperat
 
 public record SegmentRuleDefinition(SegmentRuleType Type, IReadOnlyList<SegmentConditionDefinition> Conditions, IReadOnlyList<SegmentRuleDefinition>? ChildRules = null);
 
-public class SegmentService(IMicCheckDbContext db, AuditService auditService)
+public class SegmentService(IMicCheckDbContext db, IAuditService auditService)
 {
     private const int MaxSegmentsPerProject = 100;
     private const int MaxConditionsPerSegment = 100;

src/api/MicCheck.Api/Users/DependencyRegistration.cs

@@ -0,0 +1,14 @@
+using Microsoft.AspNetCore.Identity;
+
+namespace MicCheck.Api.Users;
+
+public static class DependencyRegistration
+{
+    public static IServiceCollection AddUsersServices(this IServiceCollection services)
+    {
+        services.AddScoped<UserService>();
+        services.AddScoped<IPasswordHasher<User>, PasswordHasher<User>>();
+
+        return services;
+    }
+}

src/api/MicCheck.Api/Webhooks/CreateWebhookRequest.cs

@@ -1,14 +1,22 @@
-using FluentValidation;
+using MicCheck.Api.Common.Validation;
 
 namespace MicCheck.Api.Webhooks;
 
 public record CreateWebhookRequest(string Url, string? Secret, bool Enabled);
 
-public class CreateWebhookRequestValidator : AbstractValidator<CreateWebhookRequest>
+public class CreateWebhookRequestValidator : IModelValidator<CreateWebhookRequest>
 {
-    public CreateWebhookRequestValidator()
+    public ValidationResult Validate(CreateWebhookRequest model)
     {
-        RuleFor(x => x.Url).NotEmpty().MaximumLength(500).Must(u => Uri.TryCreate(u, UriKind.Absolute, out _))
+        var result = new ValidationResult();
-            .WithMessage("Url must be a valid absolute URL.");
+
+        if (string.IsNullOrEmpty(model.Url))
+            result.AddError(nameof(model.Url), "'Url' must not be empty.");
+        else if (model.Url.Length > 500)
+            result.AddError(nameof(model.Url), "'Url' must be 500 characters or fewer.");
+        else if (!Uri.TryCreate(model.Url, UriKind.Absolute, out _))
+            result.AddError(nameof(model.Url), "Url must be a valid absolute URL.");
+
+        return result;
     }
 }

src/api/MicCheck.Api/Webhooks/DependencyRegistration.cs

@@ -0,0 +1,17 @@
+namespace MicCheck.Api.Webhooks;
+
+public static class DependencyRegistration
+{
+    public static IServiceCollection AddWebhooksServices(this IServiceCollection services)
+    {
+        services.AddScoped<WebhookService>();
+        services.AddScoped<WebhookDispatcher>();
+        services.AddSingleton<WebhookQueue>();
+        services.AddHostedService<WebhookBackgroundService>();
+        services.AddHostedService<WebhookRetryBackgroundService>();
+        services.AddHttpClient("Webhooks", client =>
+            client.DefaultRequestHeaders.Add("User-Agent", "MicCheck-Webhook/1.0"));
+
+        return services;
+    }
+}

src/api/MicCheck.Api/Webhooks/WebhookEvent.cs

@@ -1,6 +1,6 @@
 namespace MicCheck.Api.Webhooks;
 
-public class WebhookEvent
+public record WebhookEvent
 {
     public required string EventType { get; init; }
     public int? EnvironmentId { get; init; }

tests/api/MicCheck.Api.Tests.Unit/Admin/AdminApiIntegrationTests.cs

@@ -23,7 +23,7 @@ public class AdminApiIntegrationTests
     private List<FeatureState> _featureStates = null!;
     private List<AppEnvironment> _environments = null!;
     private List<Segment> _segments = null!;
-    private Mock<AuditService> _auditService = null!;
+    private Mock<IAuditService> _auditService = null!;
     private int _organizationId;
 
     [SetUp]
@@ -50,7 +50,7 @@ public class AdminApiIntegrationTests
         _db.SetupDbSetWithGeneratedIds(c => c.SegmentConditions, []);
 
         var webhookQueue = new WebhookQueue();
-        _auditService = new Mock<AuditService>(_db.Object, null!, webhookQueue);
+        _auditService = new Mock<IAuditService>();
         _auditService.Setup(a => a.LogAsync(
             It.IsAny<string>(), It.IsAny<string>(), It.IsAny<string>(),
             It.IsAny<int>(), It.IsAny<int?>(), It.IsAny<int?>(),

tests/api/MicCheck.Api.Tests.Unit/Audit/AuditLogsControllerTests.cs

@@ -46,7 +46,7 @@ public class AuditLogsControllerTests
         _db.SetupDbSet(c => c.AuditLogs, _auditLogs);
         _db.SetupDbSet(c => c.Users, []);
 
-        var auditServiceMock = new Mock<AuditService>(_db.Object, null!, new MicCheck.Api.Webhooks.WebhookQueue());
+        var auditServiceMock = new Mock<IAuditService>();
         var auditService = auditServiceMock.Object;
 
         _controller = new AuditLogsController(

tests/api/MicCheck.Api.Tests.Unit/Environments/EnvironmentServiceTests.cs

@@ -45,7 +45,7 @@ public class EnvironmentServiceTests
         _db.SetupDbSet(c => c.Identities, _identities);
 
         var webhookQueue = new MicCheck.Api.Webhooks.WebhookQueue();
-        var auditService = new Mock<AuditService>(_db.Object, null!, webhookQueue);
+        var auditService = new Mock<IAuditService>();
         auditService.Setup(a => a.LogAsync(
             It.IsAny<string>(), It.IsAny<string>(), It.IsAny<string>(),
             It.IsAny<int>(), It.IsAny<int?>(), It.IsAny<int?>(),

tests/api/MicCheck.Api.Tests.Unit/Environments/EnvironmentsControllerTests.cs

@@ -113,7 +113,7 @@ public class EnvironmentsControllerTests
         _db.SetupDbSet(c => c.Users, []);
 
         var webhookQueue = new WebhookQueue();
-        var auditServiceMock = new Mock<AuditService>(_db.Object, null!, webhookQueue);
+        var auditServiceMock = new Mock<IAuditService>();
         auditServiceMock.Setup(a => a.LogAsync(
             It.IsAny<string>(), It.IsAny<string>(), It.IsAny<string>(),
             It.IsAny<int>(), It.IsAny<int?>(), It.IsAny<int?>(),

tests/api/MicCheck.Api.Tests.Unit/Features/FeatureEvaluationServiceTests.cs

@@ -1,6 +1,7 @@
 using System.Diagnostics.Metrics;
 using MicCheck.Api.Data;
 using MicCheck.Api.Features;
+using MicCheck.Api.Features.Usage;
 using MicCheck.Api.Identities;
 using MicCheck.Api.Segments;
 using MicCheck.Api.Tests.Unit.TestSupport;

tests/api/MicCheck.Api.Tests.Unit/Features/FeatureServiceTests.cs

@@ -45,7 +45,7 @@ public class FeatureServiceTests
         _db.SetupDbSetWithGeneratedIds(c => c.Tags, _tags);
 
         var webhookQueue = new MicCheck.Api.Webhooks.WebhookQueue();
-        var auditService = new Mock<AuditService>(_db.Object, null!, webhookQueue);
+        var auditService = new Mock<IAuditService>();
         auditService.Setup(a => a.RecordAsync(
             It.IsAny<string>(), It.IsAny<string>(), It.IsAny<string>(),
             It.IsAny<int>(), It.IsAny<int?>(), It.IsAny<int?>(),

tests/api/MicCheck.Api.Tests.Unit/Features/FeatureStateServiceTests.cs

@@ -43,7 +43,7 @@ public class FeatureStateServiceTests
         _db.SetupDbSetWithGeneratedIds(c => c.FeatureStates, _featureStates);
 
         var webhookQueue = new WebhookQueue();
-        var auditService = new Mock<AuditService>(_db.Object, null!, webhookQueue);
+        var auditService = new Mock<IAuditService>();
         auditService.Setup(a => a.RecordAsync(
             It.IsAny<string>(), It.IsAny<string>(), It.IsAny<string>(),
             It.IsAny<int>(), It.IsAny<int?>(), It.IsAny<int?>(),
@@ -154,7 +154,7 @@ public class FeatureStateServiceTests
         var state = AddState();
         var queue = new WebhookQueue();
 
-        var auditService = new Mock<AuditService>(_db.Object, null!, queue);
+        var auditService = new Mock<IAuditService>();
         auditService.Setup(a => a.RecordAsync(
             It.IsAny<string>(), It.IsAny<string>(), It.IsAny<string>(),
             It.IsAny<int>(), It.IsAny<int?>(), It.IsAny<int?>(),

tests/api/MicCheck.Api.Tests.Unit/Features/FeaturesControllerTests.cs

@@ -41,7 +41,7 @@ public class FeaturesControllerTests
         _db.SetupDbSetWithGeneratedIds(c => c.Tags, _tags);
 
         var webhookQueue = new MicCheck.Api.Webhooks.WebhookQueue();
-        var auditService = new Mock<AuditService>(_db.Object, null!, webhookQueue);
+        var auditService = new Mock<IAuditService>();
         auditService.Setup(a => a.RecordAsync(
             It.IsAny<string>(), It.IsAny<string>(), It.IsAny<string>(),
             It.IsAny<int>(), It.IsAny<int?>(), It.IsAny<int?>(),

tests/api/MicCheck.Api.Tests.Unit/Features/FlagsApiIntegrationTests.cs

@@ -2,6 +2,7 @@ using System.Security.Claims;
 using MicCheck.Api.Data;
 using MicCheck.Api.Environments;
 using MicCheck.Api.Features;
+using MicCheck.Api.Features.Usage;
 using MicCheck.Api.Identities;
 using MicCheck.Api.Projects;
 using MicCheck.Api.Segments;

tests/api/MicCheck.Api.Tests.Unit/Features/Usage/FeatureUsageControllerTests.cs

@@ -1,12 +1,12 @@
 using MicCheck.Api.Data;
-using MicCheck.Api.Features;
+using MicCheck.Api.Features.Usage;
 using MicCheck.Api.Tests.Unit.TestSupport;
 using Microsoft.AspNetCore.Mvc;
 using Microsoft.Extensions.Caching.Memory;
 using Moq;
 using NUnit.Framework;
 
-namespace MicCheck.Api.Tests.Unit.Features;
+namespace MicCheck.Api.Tests.Unit.Features.Usage;
 
 [TestFixture]
 public class FeatureUsageControllerTests

tests/api/MicCheck.Api.Tests.Unit/Features/Usage/FeatureUsageMetricsTests.cs

@@ -1,9 +1,9 @@
 using System.Diagnostics.Metrics;
-using MicCheck.Api.Features;
+using MicCheck.Api.Features.Usage;
 using Moq;
 using NUnit.Framework;
 
-namespace MicCheck.Api.Tests.Unit.Features;
+namespace MicCheck.Api.Tests.Unit.Features.Usage;
 
 [TestFixture]
 public class FeatureUsageMetricsTests

tests/api/MicCheck.Api.Tests.Unit/Features/Usage/FeatureUsageQueryServiceTests.cs

@@ -1,10 +1,10 @@
 using MicCheck.Api.Data;
-using MicCheck.Api.Features;
+using MicCheck.Api.Features.Usage;
 using MicCheck.Api.Tests.Unit.TestSupport;
 using Moq;
 using NUnit.Framework;
 
-namespace MicCheck.Api.Tests.Unit.Features;
+namespace MicCheck.Api.Tests.Unit.Features.Usage;
 
 [TestFixture]
 public class FeatureUsageQueryServiceTests

tests/api/MicCheck.Api.Tests.Unit/Identities/IdentitiesControllerTests.cs

@@ -2,6 +2,7 @@ using System.Security.Claims;
 using MicCheck.Api.Data;
 using MicCheck.Api.Environments;
 using MicCheck.Api.Features;
+using MicCheck.Api.Features.Usage;
 using MicCheck.Api.Identities;
 using MicCheck.Api.Projects;
 using MicCheck.Api.Segments;

tests/api/MicCheck.Api.Tests.Unit/Organizations/OrganizationServiceTests.cs

@@ -41,7 +41,7 @@ public class OrganizationServiceTests
         _db.SetupDbSet(c => c.Users, _users);
 
         var webhookQueue = new MicCheck.Api.Webhooks.WebhookQueue();
-        var auditService = new Mock<AuditService>(_db.Object, null!, webhookQueue);
+        var auditService = new Mock<IAuditService>();
         auditService.Setup(a => a.LogAsync(
             It.IsAny<string>(), It.IsAny<string>(), It.IsAny<string>(),
             It.IsAny<int>(), It.IsAny<int?>(), It.IsAny<int?>(),

tests/api/MicCheck.Api.Tests.Unit/Organizations/OrganizationsControllerTests.cs

@@ -49,7 +49,7 @@ public class OrganizationsControllerTests
         _db.SetupDbSetWithGeneratedIds(c => c.Webhooks, _webhooks);
 
         var webhookQueue = new WebhookQueue();
-        var auditService = new Mock<AuditService>(_db.Object, null!, webhookQueue);
+        var auditService = new Mock<IAuditService>();
         auditService.Setup(a => a.LogAsync(
             It.IsAny<string>(), It.IsAny<string>(), It.IsAny<string>(),
             It.IsAny<int>(), It.IsAny<int?>(), It.IsAny<int?>(),

tests/api/MicCheck.Api.Tests.Unit/Projects/ProjectServiceTests.cs

@@ -32,7 +32,7 @@ public class ProjectServiceTests
         _db.SetupDbSet(c => c.UserProjectPermissions, _permissions);
 
         var webhookQueue = new MicCheck.Api.Webhooks.WebhookQueue();
-        var auditService = new Mock<AuditService>(_db.Object, null!, webhookQueue);
+        var auditService = new Mock<IAuditService>();
         auditService.Setup(a => a.LogAsync(
             It.IsAny<string>(), It.IsAny<string>(), It.IsAny<string>(),
             It.IsAny<int>(), It.IsAny<int?>(), It.IsAny<int?>(),

tests/api/MicCheck.Api.Tests.Unit/Projects/ProjectsControllerTests.cs

@@ -34,7 +34,7 @@ public class ProjectsControllerTests
         _db.SetupDbSet(c => c.UserProjectPermissions, _permissions);
 
         var webhookQueue = new MicCheck.Api.Webhooks.WebhookQueue();
-        var auditService = new Mock<AuditService>(_db.Object, null!, webhookQueue);
+        var auditService = new Mock<IAuditService>();
         auditService.Setup(a => a.LogAsync(
             It.IsAny<string>(), It.IsAny<string>(), It.IsAny<string>(),
             It.IsAny<int>(), It.IsAny<int?>(), It.IsAny<int?>(),

tests/api/MicCheck.Api.Tests.Unit/Segments/SegmentServiceTests.cs

@@ -40,7 +40,7 @@ public class SegmentServiceTests
         _db.SetupDbSetWithGeneratedIds(c => c.SegmentConditions, _segmentConditions);
 
         var webhookQueue = new MicCheck.Api.Webhooks.WebhookQueue();
-        var auditService = new Mock<AuditService>(_db.Object, null!, webhookQueue);
+        var auditService = new Mock<IAuditService>();
         auditService.Setup(a => a.LogAsync(
             It.IsAny<string>(), It.IsAny<string>(), It.IsAny<string>(),
             It.IsAny<int>(), It.IsAny<int?>(), It.IsAny<int?>(),

tests/api/MicCheck.Api.Tests.Unit/Segments/SegmentsControllerTests.cs

@@ -41,7 +41,7 @@ public class SegmentsControllerTests
         _db.SetupDbSetWithGeneratedIds(c => c.SegmentConditions, _segmentConditions);
 
         var webhookQueue = new MicCheck.Api.Webhooks.WebhookQueue();
-        var auditService = new Mock<AuditService>(_db.Object, null!, webhookQueue);
+        var auditService = new Mock<IAuditService>();
         auditService.Setup(a => a.LogAsync(
             It.IsAny<string>(), It.IsAny<string>(), It.IsAny<string>(),
             It.IsAny<int>(), It.IsAny<int?>(), It.IsAny<int?>(),