MQTT connection

[Oderik]

Establish MQTT communication with server

[Oderik]

Now I prefer Async MQTT client as an alternative to PubSub, because

• it seems to be compatible to our setup (though I still have some trouble)
• I like the asynchronous approach
• it (also) features TLS

PS:

• unlike PubSub it supports all QoS levels for in and out

[Oderik]

Still work to do, but this proof of concept ticket is done.