Add support for messaging via mqtt

[normanmaurer]

At the moment there are various supported ways how to use messaging. It would be nice if you could add mqtt as well. This would allow to easy integrate with other software that could just subscribe to a topic.

[andig]

What kind of "messaging"?

[normanmaurer]

This one https://docs.evcc.io/docs/reference/configuration/messaging

So I think it is not really messaging but services that is used by messaging

[andig]

I see. That would mean adding a custom push device. Not a priority, but happy to take a PR. Doing so it would also be nice to remove the script push device- it can already be implemented using the script plugin.

/cc @GrimmiMeloni in case you're interested

[normanmaurer]

Yeah for now I just use the script stuff with mosquito_pub

[GrimmiMeloni]

Yeah, about time for me to contribute something again. ;)

@normanmaurer what would an MVP look like? Does simply configuring a broker + a topic to publish to suffice?

[normanmaurer]

@GrimmiMeloni yes 🎉

[andig]

Spannend ist noch wie wir mit title und msg umgehen. Vllt. Lassen wir bei den custom Integrationen einfach den title weg?

[normanmaurer]

Or we could also use json for the payload

[andig]

Like it. Could be an encoding option on the custom messenger.

[GrimmiMeloni]

I am wondering why we are talking custom here? I was planning to just add an mqtt flavor to the list of supported messaging services (shoutr, telegram, ....)

[andig]

I just thought we have custom everywhere and script already is a custom integration. Why not make it fully flexible before the next user wants http?

[GrimmiMeloni]

OK. But if we already have a custom solution via script, then what is actually missing here? Sorry for being "stupid", but I still don't understand the actual ask. Can you maybe show an example of the configuration you expect, or some other fragment that explains what the difference between script and custom would be?