Add option to disable relay reporting to MQTT

[Niek]

This feature is especially useful when using custom MQTT groups for relays. This adds the option to disable the reporting of relay statuses to MQTT, and report only to the custom MQTT groups (if defined).

[Niek]

It might make sense to change all mqttForward() calls in the code as well (which is determined by a check if MQTT_GETTER != MQTT_SETTER - I don't really understand the logic there).

[mcspr]

which is determined by a check if MQTT_GETTER != MQTT_SETTER - I don't really understand the logic there

For example, if both are empty (and therefore equal), we are subscribed to the <root>/relay/0 and will also use it to send our state.

[Niek]

which is determined by a check if MQTT_GETTER != MQTT_SETTER - I don't really understand the logic there

For example, if both are empty (and therefore equal), we are subscribed to the <root>/relay/0 and will also use it to send our state.

OK that makes sense - I changed the code to use mqttForward() instead.

[mcspr]

@Niek mqttForward() is not always available. 300KiB builds break because of that:
https://travis-ci.org/mcspr/espurna-nightly-builder/jobs/512070680#L984-L990

[Niek]

Ah I didn't think of that, what do you think would be the cleaned approach? Make a dummy mqttForward() function in relay.ino in case MQTT_SUPPORT is false? Or duplicate those calls with if #MQTT_SUPPORT blocks around it?

[Niek]

I submitted a fix in PR #1662

[mcspr]

IDK though why it must depend on it. Forwarding setting is only ever checked when relay status (or light, or domoticz) function is called from within MQTT callback, so that we do not report back to the same topic we just received data from. Now, it is always called.
Heartbeat mechanism also can send all relays status, which forwarding setting && new define does not stop, but it can be disabled at runtime or via define flag default (see HEARTBEAT_REPORT_RELAY in utils)
So maybe it should do something similar and just check in relayMqtt(id) new optional setting / define and do nothing (report=false and no send)? Or there can be a more elaborate reporting mechanism, following the idea of broker module.

edit: words