build: update build configuration to use internal metadata package and improve ldflags injection, fix defer resp.Body.Close() usage, replace os.Setenv with t.Setenv in tests, correct error message casing, and adjust Dockerfile and Makefile for cmd/reloader structure

internal/pkg/webhook/webhook.go

@@ -73,7 +73,7 @@ func (c *Client) Send(ctx context.Context, payload Payload) error {
 	if err != nil {
 		return fmt.Errorf("sending request: %w", err)
 	}
-	defer resp.Body.Close()
+	defer func() { _ = resp.Body.Close() }()
 
 	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
 		return fmt.Errorf("webhook returned status %d", resp.StatusCode)

internal/pkg/webhook/webhook_test.go

@@ -74,7 +74,7 @@ func TestSend_MarshalPayload(t *testing.T) {
 
 	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		body, _ := io.ReadAll(r.Body)
-		json.Unmarshal(body, &receivedPayload)
+		_ = json.Unmarshal(body, &receivedPayload)
 		w.WriteHeader(http.StatusOK)
 	}))
 	defer server.Close()