fix: Ensure open api tool service account exchanger uses quota project id for ADC

gcloud auth team requested that we audit ADK's codebase for places where ADC (google.auth.default) is used, and make sure that the quota project id header is being populated.

Co-authored-by: Kathy Wu <wukathy@google.com>
PiperOrigin-RevId: 855322964

tests/unittests/tools/openapi_tool/openapi_spec_parser/test_rest_api_tool.py

@@ -25,6 +25,10 @@ from fastapi.openapi.models import Operation
 from fastapi.openapi.models import Parameter as OpenAPIParameter
 from fastapi.openapi.models import RequestBody
 from fastapi.openapi.models import Schema as OpenAPISchema
+from google.adk.auth.auth_credential import AuthCredential
+from google.adk.auth.auth_credential import AuthCredentialTypes
+from google.adk.auth.auth_credential import HttpAuth
+from google.adk.auth.auth_credential import HttpCredentials
 from google.adk.sessions.state import State
 from google.adk.tools.openapi_tool.auth.auth_helpers import token_to_scheme_credential
 from google.adk.tools.openapi_tool.common.common import ApiParameter
@@ -721,6 +725,35 @@ class TestRestApiTool:
 
     assert request_params["cookies"]["session_id"] == "cookie_value"
 
+  def test_prepare_request_params_quota_project_id(
+      self,
+      sample_endpoint,
+      sample_operation,
+      sample_auth_scheme,
+  ):
+    auth_credential = AuthCredential(
+        auth_type=AuthCredentialTypes.HTTP,
+        http=HttpAuth(
+            scheme="bearer",
+            credentials=HttpCredentials(),
+            additional_headers={"x-goog-user-project": "test-project"},
+        ),
+    )
+    tool = RestApiTool(
+        name="test_tool",
+        description="Test Tool",
+        endpoint=sample_endpoint,
+        operation=sample_operation,
+        auth_credential=auth_credential,
+        auth_scheme=sample_auth_scheme,
+    )
+    params = []
+    kwargs = {}
+
+    request_params = tool._prepare_request_params(params, kwargs)
+
+    assert request_params["headers"]["x-goog-user-project"] == "test-project"
+
   def test_prepare_request_params_multiple_mime_types(
       self, sample_endpoint, sample_auth_credential, sample_auth_scheme
   ):