Override compute_region_url_maps_v1::RegionUrlMapsClient Endpoint Configuration

  // This configuration is common with Private Google Access:
  //     https://cloud.google.com/vpc/docs/private-google-access
  auto options = google::cloud::Options{}.set<google::cloud::EndpointOption>(
      "private.googleapis.com");
  auto client = google::cloud::compute_region_url_maps_v1::RegionUrlMapsClient(
      google::cloud::ExperimentalTag{},
      google::cloud::compute_region_url_maps_v1::
          MakeRegionUrlMapsConnectionRest(google::cloud::ExperimentalTag{},
                                          options));