[FEATURE] Message persistence in MQTT

[lewsut]

Describe the feature
Option in MQTT Publish tag options for message persistence flag to be set.

[unocelli]

@lewsut Hi, I will add it fix in the code and not configurable, what do you think about?

[lewsut]

@unocelli I think I can solve this at the MQTT server side, I don't want to for people to use something that could be detrimental. Sometimes you want clean tags / messages.

I'll have a go and close this if I succeed.

[lewsut]

Can't test this yet as git clone via docker doesn't pull the newest commit for a few days ...

[lewsut]

@unocelli your solution works well