feat: add auto_populated_fields to google.api.MethodSettings

PiperOrigin-RevId: 586359350

google/api/client.proto

@@ -349,6 +349,19 @@ message MethodSettings {
   //          total_poll_timeout:
   //             seconds: 54000 # 90 minutes
   LongRunning long_running = 2;
+
+  // List of top-level fields of the request message, that should be
+  // automatically populated by the client libraries based on their
+  // (google.api.field_info).format. Currently supported format: UUID4.
+  //
+  // Example of a YAML configuration:
+  //
+  //  publishing:
+  //    method_settings:
+  //      - selector: google.example.v1.ExampleService.CreateExample
+  //        auto_populated_fields:
+  //        - request_id
+  repeated string auto_populated_fields = 3;
 }
 
 // The organization for which the client libraries are being published.