support LWT (Last Will and Testament) about mqtt-io

[flyte]

I guess it's not a big deal to make it configurable, so I'll do that.

[flyte]

Sure, that's a good idea. Does it have to be configurable, or will the following suffice:

• Status topic at <prefix>/status
• Publish (retained) on start up: running
• Publish (retained) when exiting: stopped
• Last will in case of unclean disconnection: dead

[flyte]

@CWempe I've added this functionality, so please test with version 0.1.0. Cheers!

PS. Check the bottom of the readme for config values.

[vontrapp]

Can LWT be used to set many topics on death? It would be great if I could use that to clear any retained inputs when it is disconnected.

Or maybe there's another mqtt feature that does the same?

[flyte]

@vontrapp I don't think so. This is a good article on the subject:
https://www.hivemq.com/blog/mqtt-essentials-part-9-last-will-and-testament

If you want to clear retained messages when it's disconnected, would just setting retain = false work?