code: public Observable<OperationStatus> addAsync(UUID appId, AddPermissionsOptionalParameter addOptionalParameter) {
          return addWithServiceResponseAsync(appId, addOptionalParameter).map(new Func1<ServiceResponse<OperationStatus>, OperationStatus>() {
              @Override
              public OperationStatus call(ServiceResponse<OperationStatus> response) {
                  return response.body();
              }
          });
      }
docs: Adds a user to the allowed list of users to access this LUIS application. Users are added using their email address.
  
  @param appId The application ID.
  @param addOptionalParameter the object representing the optional parameters to be set before calling this API
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the OperationStatus object