Smarthome integration should expose DisconnectResponse

[proppy]

Currently it seems that smarthome integration always returns an empty response for DisconnectRequest.

https://github.com/actions-on-google/actions-on-google-java/blob/master/src/main/kotlin/com/google/actions/api/smarthome/SmartHomeApp.kt#L166

This could be problematic as developer might need to return an errorCode when the DisconnectRequest is failing.

[Fleker]

According to the documentation there is no errorCode field for a DisconnectResponse type.

[proppy]

Yes but https://developers.google.com/assistant/smarthome/develop/process-intents seems to indicate that most response could return errorCode

[Fleker]

This should be clarified more precisely. Even if the DisconnectResponse provided an error code, I don't believe the platform will interpret it. Regardless it seems like it'll disconnect the service.