feat(generator): use setup_request_id from api_core

Author: hebaalazzeh

packages/gapic-generator/gapic/templates/%namespace/%name_%version/%sub/services/%service/client.py.j2

@@ -463,6 +463,14 @@ class {{ service.client_name }}(metaclass={{ service.client_name }}Meta):
             field_name (str): The name of the field to populate.
             is_proto3_optional (bool): Whether the field is proto3 optional.
         """
+        try:
+            from google.api_core.gapic_v1.routing_header import setup_request_id
+            return setup_request_id(request, field_name, is_proto3_optional)
+        except ImportError:
+            pass
+
+        # TODO(issue #17813): remove fallback once google-api-core >= 2.26.0 is required
+        # pragma: NO COVER
         if isinstance(request, dict):
             if is_proto3_optional:
                 if field_name not in request:

packages/gapic-generator/tests/integration/goldens/storagebatchoperations/google/cloud/storagebatchoperations_v1/services/storage_batch_operations/client.py

@@ -480,6 +480,14 @@ def _setup_request_id(request, field_name: str, is_proto3_optional: bool):
             field_name (str): The name of the field to populate.
             is_proto3_optional (bool): Whether the field is proto3 optional.
         """
+        try:
+            from google.api_core.gapic_v1.routing_header import setup_request_id
+            return setup_request_id(request, field_name, is_proto3_optional)
+        except ImportError:
+            pass
+
+        # TODO(issue #17813): remove fallback once google-api-core >= 2.26.0 is required
+        # pragma: NO COVER
         if isinstance(request, dict):
             if is_proto3_optional:
                 if field_name not in request: