fix: issue 3785. id_token missing

src/google/adk/auth/auth_credential.py

@@ -76,6 +76,7 @@ class OAuth2Auth(BaseModelWithConfig):
   auth_response_uri: Optional[str] = None
   auth_code: Optional[str] = None
   access_token: Optional[str] = None
+  id_token: Optional[str] = None
   refresh_token: Optional[str] = None
   expires_at: Optional[int] = None
   expires_in: Optional[int] = None

src/google/adk/auth/oauth2_credential_util.py

@@ -108,6 +108,7 @@ def update_credential_with_tokens(
   """
   auth_credential.oauth2.access_token = tokens.get("access_token")
   auth_credential.oauth2.refresh_token = tokens.get("refresh_token")
+  auth_credential.oauth2.id_token = tokens.get("id_token", None)
   auth_credential.oauth2.expires_at = (
       int(tokens.get("expires_at")) if tokens.get("expires_at") else None
   )