The `DisableGatewayService` field on the `NetworkDriver.Join` is not documented

Documentation of the https://github.com/moby/libnetwork/blob/master/docs/remote.md#join `NetworkDriver.Join` response does not list the `DisableGatewayService` field, but apparently it's supported in the GO implementation (https://github.com/moby/libnetwork/blob/master/drivers/remote/api/api.go#L175) 

Is this an officially supported field? If so I suggest to add it to the documentation.