test(api): add feature handler tests for regular and mixed keys

Add tests for UpdateFeatures endpoint covering:
- Regular feature flag keys with various value types
- Mixed keys combining feature flags with log retention settings
- Redis storage verification for both scenarios

internal/api/feature_handler_test.go

@@ -93,6 +93,98 @@ func TestFeatureHandler_UpdateFeatures_LogOverridesClear(t *testing.T) {
 	}
 }
 
+func TestFeatureHandler_UpdateFeatures_RegularKeys(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+
+	mr := miniredis.RunT(t)
+	rdb := redis.NewClient(&redis.Options{Addr: mr.Addr()})
+
+	h := NewFeatureHandler(rdb)
+	r := gin.New()
+	r.PUT("/admin/features", h.UpdateFeatures)
+
+	body := []byte(`{"dp_context_preflight_enabled":false,"dp_state_store_backend":"redis","dp_claude_cross_upstream":"false","custom_number":12}`)
+	req := httptest.NewRequest(http.MethodPut, "/admin/features", bytes.NewReader(body))
+	rr := httptest.NewRecorder()
+	r.ServeHTTP(rr, req)
+
+	if rr.Code != http.StatusOK {
+		t.Fatalf("expected 200, got %d body=%s", rr.Code, rr.Body.String())
+	}
+
+	var got struct {
+		Updated map[string]string `json:"updated"`
+	}
+	if err := json.Unmarshal(rr.Body.Bytes(), &got); err != nil {
+		t.Fatalf("decode response: %v", err)
+	}
+	if got.Updated["dp_context_preflight_enabled"] != "false" {
+		t.Fatalf("expected dp_context_preflight_enabled=false, got %q", got.Updated["dp_context_preflight_enabled"])
+	}
+	if got.Updated["dp_state_store_backend"] != "redis" {
+		t.Fatalf("expected dp_state_store_backend=redis, got %q", got.Updated["dp_state_store_backend"])
+	}
+	if got.Updated["dp_claude_cross_upstream"] != "false" {
+		t.Fatalf("expected dp_claude_cross_upstream=false, got %q", got.Updated["dp_claude_cross_upstream"])
+	}
+	if got.Updated["custom_number"] != "12" {
+		t.Fatalf("expected custom_number=12, got %q", got.Updated["custom_number"])
+	}
+
+	if v := mr.HGet("meta:features", "dp_context_preflight_enabled"); v != "false" {
+		t.Fatalf("expected redis dp_context_preflight_enabled=false, got %q", v)
+	}
+	if v := mr.HGet("meta:features", "dp_state_store_backend"); v != "redis" {
+		t.Fatalf("expected redis dp_state_store_backend=redis, got %q", v)
+	}
+	if v := mr.HGet("meta:features", "dp_claude_cross_upstream"); v != "false" {
+		t.Fatalf("expected redis dp_claude_cross_upstream=false, got %q", v)
+	}
+	if v := mr.HGet("meta:features", "custom_number"); v != "12" {
+		t.Fatalf("expected redis custom_number=12, got %q", v)
+	}
+}
+
+func TestFeatureHandler_UpdateFeatures_MixedKeys(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+
+	mr := miniredis.RunT(t)
+	rdb := redis.NewClient(&redis.Options{Addr: mr.Addr()})
+
+	h := NewFeatureHandler(rdb)
+	r := gin.New()
+	r.PUT("/admin/features", h.UpdateFeatures)
+
+	body := []byte(`{"dp_context_preflight_enabled":true,"log_retention_days":5}`)
+	req := httptest.NewRequest(http.MethodPut, "/admin/features", bytes.NewReader(body))
+	rr := httptest.NewRecorder()
+	r.ServeHTTP(rr, req)
+
+	if rr.Code != http.StatusOK {
+		t.Fatalf("expected 200, got %d body=%s", rr.Code, rr.Body.String())
+	}
+
+	var got struct {
+		Updated map[string]string `json:"updated"`
+	}
+	if err := json.Unmarshal(rr.Body.Bytes(), &got); err != nil {
+		t.Fatalf("decode response: %v", err)
+	}
+	if got.Updated["dp_context_preflight_enabled"] != "true" {
+		t.Fatalf("expected dp_context_preflight_enabled=true, got %q", got.Updated["dp_context_preflight_enabled"])
+	}
+	if got.Updated["log_retention_days"] != "5" {
+		t.Fatalf("expected log_retention_days=5, got %q", got.Updated["log_retention_days"])
+	}
+
+	if v := mr.HGet("meta:features", "dp_context_preflight_enabled"); v != "true" {
+		t.Fatalf("expected redis dp_context_preflight_enabled=true, got %q", v)
+	}
+	if v, _ := mr.Get("meta:log:retention_days"); v != "5" {
+		t.Fatalf("expected redis retention_days=5, got %q", v)
+	}
+}
+
 func TestFeatureHandler_ListFeatures_IncludesLogOverrides(t *testing.T) {
 	gin.SetMode(gin.TestMode)