Add Serilog console logging across the API

Information at endpoint and service-method boundaries, Debug in deeper
helpers, Warning before expected/recoverable failures (not-found,
validation, agent tool errors), Error on caught exceptions. Serilog
wraps the exception handler so request-completion logs report the
resolved status code rather than the raw exception. Never logs prose
bodies or the Anthropic API key.

src/Novelly.Api/Chapters/ChapterEndpoints.cs

@@ -1,10 +1,12 @@
+using Novelly.Api.Common;
+
 namespace Novelly.Api.Chapters;
 
 public static class ChapterEndpoints
 {
     public static IEndpointRouteBuilder MapChapterEndpoints(this IEndpointRouteBuilder app)
     {
-        var projectScoped = app.MapGroup("/api/projects/{projectId:guid}/chapters").WithTags("Chapters");
+        var projectScoped = app.MapGroup("/api/projects/{projectId:guid}/chapters").WithTags("Chapters").AddEndpointFilter<RequestLoggingEndpointFilter>();
 
         projectScoped.MapGet("/", async (Guid projectId, ChapterService service, CancellationToken ct) =>
                 Results.Ok(await service.ListAsync(projectId, ct)))
@@ -18,7 +20,7 @@ public static class ChapterEndpoints
             })
             .WithSummary("Add a chapter.");
 
-        var chapters = app.MapGroup("/api/chapters").WithTags("Chapters");
+        var chapters = app.MapGroup("/api/chapters").WithTags("Chapters").AddEndpointFilter<RequestLoggingEndpointFilter>();
 
         chapters.MapGet("/{id:guid}", async (Guid id, ChapterService service, CancellationToken ct) =>
                 Results.Ok(await service.GetAsync(id, ct)))

src/Novelly.Api/Chapters/ChapterService.cs

@@ -6,10 +6,12 @@ using Novelly.Api.Tags;
 
 namespace Novelly.Api.Chapters;
 
-public class ChapterService(INovelDbContext db, TagService tags)
+public class ChapterService(INovelDbContext db, TagService tags, ILogger<ChapterService> logger)
 {
     public async Task<IReadOnlyList<ChapterSummaryDto>> ListAsync(Guid projectId, CancellationToken ct = default)
     {
+        logger.LogInformation("Listing chapters for project {ProjectId}", projectId);
+
         var chapters = await db.Chapters
             .Include(c => c.PovCharacter)
             .Include(c => c.Beats)
@@ -22,13 +24,19 @@ public class ChapterService(INovelDbContext db, TagService tags)
         return [.. chapters.Select(c => c.ToSummaryDto())];
     }
 
-    public async Task<ChapterDto> GetAsync(Guid id, CancellationToken ct = default) =>
-        (await FindAsync(id, ct)).ToDto();
+    public async Task<ChapterDto> GetAsync(Guid id, CancellationToken ct = default)
+    {
+        logger.LogInformation("Getting chapter {ChapterId}", id);
+        return (await FindAsync(id, ct)).ToDto();
+    }
 
     public async Task<ChapterDto> CreateAsync(Guid projectId, CreateChapterRequest request, CancellationToken ct = default)
     {
+        logger.LogInformation("Creating chapter {Title} for project {ProjectId}", request.Title, projectId);
+
         if (!await db.Projects.AnyAsync(p => p.Id == projectId, ct))
         {
+            logger.LogWarning("Project {ProjectId} not found", projectId);
             throw new NotFoundException(nameof(Project), projectId);
         }
 
@@ -57,6 +65,8 @@ public class ChapterService(INovelDbContext db, TagService tags)
 
     public async Task<ChapterDto> UpdateAsync(Guid id, UpdateChapterRequest request, CancellationToken ct = default)
     {
+        logger.LogInformation("Updating chapter {ChapterId}", id);
+
         var chapter = await FindAsync(id, ct);
 
         chapter.Title = Patch.Apply(chapter.Title, request.Title) ?? chapter.Title;
@@ -80,6 +90,8 @@ public class ChapterService(INovelDbContext db, TagService tags)
 
     public async Task DeleteAsync(Guid id, CancellationToken ct = default)
     {
+        logger.LogInformation("Deleting chapter {ChapterId}", id);
+
         var chapter = await FindAsync(id, ct);
         db.Chapters.Remove(chapter);
         await db.SaveChangesAsync(ct);
@@ -87,21 +99,37 @@ public class ChapterService(INovelDbContext db, TagService tags)
 
     private async Task<int> NextChapterNumberAsync(Guid projectId, CancellationToken ct)
     {
+        logger.LogDebug("Computing next chapter number for project {ProjectId}", projectId);
+
         var max = await db.Chapters
             .Where(c => c.ProjectId == projectId)
             .MaxAsync(c => (int?)c.Number, ct);
 
-        return (max ?? 0) + 1;
+        var next = (max ?? 0) + 1;
+        logger.LogDebug("Next chapter number for project {ProjectId} is {Number}", projectId, next);
+        return next;
     }
 
-    private async Task<Chapter> FindAsync(Guid id, CancellationToken ct) =>
-        await db.Chapters
+    private async Task<Chapter> FindAsync(Guid id, CancellationToken ct)
+    {
+        logger.LogDebug("Finding chapter {ChapterId}", id);
+
+        var chapter = await db.Chapters
             .Include(c => c.PovCharacter)
             .Include(c => c.Beats).ThenInclude(b => b.Character)
             .Include(c => c.Beats).ThenInclude(b => b.Scene)
             .Include(c => c.Beats).ThenInclude(b => b.Tags)
             .Include(c => c.Scenes).ThenInclude(s => s.PovCharacter)
             .Include(c => c.Tags)
-            .FirstOrDefaultAsync(c => c.Id == id, ct)
-        ?? throw new NotFoundException(nameof(Chapter), id);
+            .FirstOrDefaultAsync(c => c.Id == id, ct);
+
+        if (chapter is null)
+        {
+            logger.LogWarning("Chapter {ChapterId} not found", id);
+            throw new NotFoundException(nameof(Chapter), id);
+        }
+
+        logger.LogDebug("Found chapter {ChapterId}", id);
+        return chapter;
+    }
 }