fix: fallback to project id if crendetials don't contain quota project

Co-authored-by: Kathy Wu <wukathy@google.com>
PiperOrigin-RevId: 914934690

Author: wukath

src/google/adk/integrations/agent_registry/agent_registry.py

@@ -208,7 +208,10 @@ def _get_auth_headers(self) -> Dict[str, str]:
           "Authorization": f"Bearer {self._credentials.token}",
           "Content-Type": "application/json",
       }
-      quota_project_id = getattr(self._credentials, "quota_project_id", None)
+      quota_project_id = (
+          getattr(self._credentials, "quota_project_id", None)
+          or self.project_id
+      )
       if quota_project_id:
         headers["x-goog-user-project"] = quota_project_id
       return headers

tests/unittests/integrations/agent_registry/test_agent_registry.py

@@ -607,6 +607,15 @@ def test_get_auth_headers(self, registry):
     assert headers["Authorization"] == "Bearer fake-token"
     assert headers["x-goog-user-project"] == "quota-project"
 
+  def test_get_auth_headers_fallback_to_project_id(self, registry):
+    registry._credentials.token = "fake-token"
+    registry._credentials.refresh = MagicMock()
+    registry._credentials.quota_project_id = None
+
+    headers = registry._get_auth_headers()
+    assert headers["Authorization"] == "Bearer fake-token"
+    assert headers["x-goog-user-project"] == "test-project"
+
   @patch("httpx.Client")
   def test_make_request_raises_http_status_error(self, mock_httpx, registry):
     mock_response = MagicMock()