feat: add service_account_email for export subscriptions

protos/google/pubsub/v1/pubsub.proto

@@ -1141,6 +1141,14 @@ message BigQueryConfig {
   // write to in BigQuery. `use_table_schema` and `use_topic_schema` cannot be
   // enabled at the same time.
   bool use_table_schema = 6 [(google.api.field_behavior) = OPTIONAL];
+
+  // Optional. The service account to use to write to BigQuery. The subscription
+  // creator or updater that specifies this field must have
+  // `iam.serviceAccounts.actAs` permission on the service account. If not
+  // specified, the Pub/Sub [service
+  // agent](https://cloud.google.com/iam/docs/service-agents),
+  // service-{project_number}@gcp-sa-pubsub.iam.gserviceaccount.com, is used.
+  string service_account_email = 7 [(google.api.field_behavior) = OPTIONAL];
 }
 
 // Configuration for a Cloud Storage subscription.
@@ -1227,6 +1235,14 @@ message CloudStorageConfig {
   // Output only. An output-only field that indicates whether or not the
   // subscription can receive messages.
   State state = 9 [(google.api.field_behavior) = OUTPUT_ONLY];
+
+  // Optional. The service account to use to write to Cloud Storage. The
+  // subscription creator or updater that specifies this field must have
+  // `iam.serviceAccounts.actAs` permission on the service account. If not
+  // specified, the Pub/Sub
+  // [service agent](https://cloud.google.com/iam/docs/service-agents),
+  // service-{project_number}@gcp-sa-pubsub.iam.gserviceaccount.com, is used.
+  string service_account_email = 11 [(google.api.field_behavior) = OPTIONAL];
 }
 
 // A message and its corresponding acknowledgment ID.