Add unit tests for Environments namespace (0% to 99.5% coverage)

Covers EnvironmentService (CRUD, clone, list, find-by-key), the
EnvironmentsController orchestration layer (webhooks, audit logs,
identities/traits, feature states, feature segments, identity
segments), EnvironmentDocumentService/Controller, response mappers,
and request validators.

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

@@ -0,0 +1,63 @@
+using MicCheck.Api.Environments;
+using MicCheck.Api.Segments;
+using NUnit.Framework;
+
+namespace MicCheck.Api.Tests.Unit.Environments;
+
+[TestFixture]
+public class SegmentDocumentResponseTests
+{
+    [Test]
+    public void WhenMappingASegment_ThenOnlyTopLevelRulesAreIncluded()
+    {
+        var segment = new Segment { Id = 1, Name = "Beta Users", ProjectId = 1, CreatedAt = DateTimeOffset.UtcNow };
+        var topLevelRule = new SegmentRule { Id = 1, SegmentId = 1, Type = SegmentRuleType.All };
+        var nestedRule = new SegmentRule { Id = 2, SegmentId = 1, ParentRuleId = 1, Type = SegmentRuleType.Any };
+        segment.Rules.Add(topLevelRule);
+        segment.Rules.Add(nestedRule);
+
+        var response = SegmentDocumentResponse.From(segment);
+
+        Assert.That(response.Id, Is.EqualTo(1));
+        Assert.That(response.Name, Is.EqualTo("Beta Users"));
+        Assert.That(response.Rules, Has.Count.EqualTo(1));
+        Assert.That(response.Rules[0].Id, Is.EqualTo(1));
+    }
+}
+
+[TestFixture]
+public class SegmentRuleDocumentResponseTests
+{
+    [Test]
+    public void WhenMappingARule_ThenTypeIsUpperInvariantAndChildRulesAreIncluded()
+    {
+        var rule = new SegmentRule { Id = 1, SegmentId = 1, Type = SegmentRuleType.Any };
+        var condition = new SegmentCondition { Id = 1, RuleId = 1, Property = "plan", Operator = SegmentConditionOperator.Equal, Value = "pro" };
+        var childRule = new SegmentRule { Id = 2, SegmentId = 1, ParentRuleId = 1, Type = SegmentRuleType.All };
+        rule.Conditions.Add(condition);
+        rule.ChildRules.Add(childRule);
+
+        var response = SegmentRuleDocumentResponse.From(rule);
+
+        Assert.That(response.Type, Is.EqualTo("ANY"));
+        Assert.That(response.Conditions, Has.Count.EqualTo(1));
+        Assert.That(response.Rules, Has.Count.EqualTo(1));
+        Assert.That(response.Rules[0].Id, Is.EqualTo(2));
+    }
+}
+
+[TestFixture]
+public class SegmentConditionDocumentResponseTests
+{
+    [Test]
+    public void WhenMappingACondition_ThenPropertyOperatorAndValueAreCopied()
+    {
+        var condition = new SegmentCondition { Id = 1, RuleId = 1, Property = "plan", Operator = SegmentConditionOperator.Contains, Value = "pro" };
+
+        var response = SegmentConditionDocumentResponse.From(condition);
+
+        Assert.That(response.Property, Is.EqualTo("plan"));
+        Assert.That(response.Operator, Is.EqualTo("Contains"));
+        Assert.That(response.Value, Is.EqualTo("pro"));
+    }
+}