fix(receiver): return Payload as JSON object instead of string

Changed the API response to embed Payload as a JSON object using
json.RawMessage instead of returning it as a JSON-encoded string
inside the JSON response. Added MetricResponse type with ToResponse
converter method.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

internal/receiver/handler.go

@@ -74,8 +74,14 @@ func (h *Handler) handleGetByWorkflowJob(w http.ResponseWriter, r *http.Request)
 		return
 	}
 
+	// Convert to response type with Payload as JSON object
+	response := make([]MetricResponse, len(metrics))
+	for i, m := range metrics {
+		response[i] = m.ToResponse()
+	}
+
 	w.Header().Set("Content-Type", "application/json")
-	_ = json.NewEncoder(w).Encode(metrics)
+	_ = json.NewEncoder(w).Encode(response)
 }
 
 func (h *Handler) handleHealth(w http.ResponseWriter, r *http.Request) {

internal/receiver/handler_test.go

@@ -125,7 +125,7 @@ func TestHandler_GetByWorkflowJob(t *testing.T) {
 		t.Errorf("status = %d, want %d", rec.Code, http.StatusOK)
 	}
 
-	var metrics []Metric
+	var metrics []MetricResponse
 	if err := json.NewDecoder(rec.Body).Decode(&metrics); err != nil {
 		t.Fatalf("failed to decode response: %v", err)
 	}
@@ -149,7 +149,7 @@ func TestHandler_GetByWorkflowJob_NotFound(t *testing.T) {
 		t.Errorf("status = %d, want %d", rec.Code, http.StatusOK)
 	}
 
-	var metrics []Metric
+	var metrics []MetricResponse
 	if err := json.NewDecoder(rec.Body).Decode(&metrics); err != nil {
 		t.Fatalf("failed to decode response: %v", err)
 	}

internal/receiver/store.go

@@ -24,6 +24,32 @@ type Metric struct {
 	Payload      string    `gorm:"type:text;not null"` // JSON-encoded RunSummary
 }
 
+// MetricResponse is the API response type with Payload as embedded JSON object
+type MetricResponse struct {
+	ID           uint            `json:"id"`
+	Organization string          `json:"organization"`
+	Repository   string          `json:"repository"`
+	Workflow     string          `json:"workflow"`
+	Job          string          `json:"job"`
+	RunID        string          `json:"run_id"`
+	ReceivedAt   time.Time       `json:"received_at"`
+	Payload      json.RawMessage `json:"payload"`
+}
+
+// ToResponse converts a Metric to a MetricResponse with Payload as JSON object
+func (m *Metric) ToResponse() MetricResponse {
+	return MetricResponse{
+		ID:           m.ID,
+		Organization: m.Organization,
+		Repository:   m.Repository,
+		Workflow:     m.Workflow,
+		Job:          m.Job,
+		RunID:        m.RunID,
+		ReceivedAt:   m.ReceivedAt,
+		Payload:      json.RawMessage(m.Payload),
+	}
+}
+
 // Store handles SQLite storage for metrics using GORM
 type Store struct {
 	db *gorm.DB