- return PID when sending and subscribing, allow to subscribe
to a special event when receiving acknowledgement from the broker
(separate from normal lifecycle callback, since we allow a generic callable)
- rework HomeAssistant to publish with QoS 1 and wait until the broker responds.
lwmqtt sync library already did that, so this change only affects async library
- re-add `ha.send` command
- don't send HomeAssistant config when disabled, unless requested
- some more comments