fix: Support passing credentials to GCPSkillRegistry

This change allows users to pass custom credentials when initializing the GCPSkillRegistry.

Co-authored-by: Kathy Wu <wukathy@google.com>
PiperOrigin-RevId: 947335970

Author: wukath

src/google/adk/integrations/skill_registry/gcp_skill_registry.py

@@ -28,6 +28,7 @@
 from google.adk.utils import _mtls_utils
 import google.auth
 import google.auth.credentials
+from google.auth.credentials import Credentials
 import google.auth.exceptions
 from google.auth.transport import mtls
 from google.auth.transport import requests as auth_requests
@@ -42,16 +43,17 @@ def __init__(
       *,
       project_id: str | None = None,
       location: str | None = None,
+      credentials: Credentials | None = None,
   ):
     """Initializes the GCP Skill Registry.
 
     Args:
       project_id: Optional GCP project ID. If omitted, loads from environment.
       location: Optional GCP location. If omitted, loads from environment.
+      credentials: Optional credentials to use for the client.
     """
     self.project_id = project_id or os.environ.get("GOOGLE_CLOUD_PROJECT")
     self.location = location or os.environ.get("GOOGLE_CLOUD_LOCATION")
-
     # Set up SSL context for mTLS if needed
     self._ssl_context = None
     use_client_cert = _mtls_utils.use_client_cert_effective()
@@ -97,7 +99,7 @@ def __init__(
           "project_id and location must be specified or set via environment"
           " variables."
       )
-    self._credentials: google.auth.credentials.Credentials | None = None
+    self._credentials: Credentials | None = credentials
 
   async def _get_headers(self) -> dict[str, str]:
     """Refreshes credentials and returns authorization headers."""

tests/unittests/integrations/skill_registry/test_gcp_skill_registry.py

@@ -378,3 +378,33 @@ async def mock_get(url, *unused_args, **kwargs):
 
 
 # pylint: enable=protected-access
+
+
+@pytest.mark.asyncio
+async def test_use_custom_credentials():
+  """Verifies that custom credentials are used when provided."""
+  mock_creds = mock.MagicMock()
+  mock_creds.valid = True
+  mock_creds.token = "custom-token"
+  mock_creds.quota_project_id = "custom-quota-project"
+
+  registry = gcp_skill_registry.GCPSkillRegistry(credentials=mock_creds)
+
+  mock_response = mock.MagicMock()
+  mock_response.status_code = 200
+  mock_response.json.return_value = {"skills": []}
+
+  with mock.patch(
+      "httpx.AsyncClient.get", return_value=mock_response
+  ) as mock_get_called:
+    await registry.search_skills(query="query")
+
+  mock_get_called.assert_called_once_with(
+      "https://agentregistry.googleapis.com/v1alpha/projects/test-project/locations/us-central1/skills:search",
+      headers={
+          "Authorization": "Bearer custom-token",
+          "Content-Type": "application/json",
+          "x-goog-user-project": "custom-quota-project",
+      },
+      params={"search_string": "query"},
+  )