Describe the bug

To Reproduce
Steps to reproduce the behavior:

1. Setup rhai script:

fn process_request(request) {
  print(`${request.body.operation_name}`);
}

fn supergraph_service(service) {
  // Rhai convention for creating a function pointer
  const request_callback = Fn("process_request"); 
  
  service.map_request(request_callback);
}

2. Send request without operationName:

curl -H 'Content-Type: application/json' http://127.0.0.1:4000/ -d '{ "query": "query OperationName { me { id } }" }'

3. See that the rhai script printed an empty operation name.

Expected behavior
Expected request.body.operation_name to be OperationName

Additional context
Currently, request.body.operation_name is a direct copy of operationName from the client request.
But this behavior is very confusing to customers who expect it to have an operation name, if any, extracted from the query.