Improve MQTT connection failure handling

[Endymion78]

Previously, linux2mqtt stopped if MQTT broker was unavailable on startup.
Also, metrics online statuses were sent on first connection to MQTT broker only, so metrics stayed offline in case of broker restart.

This proposal modifies the code to avoid stopping execution if connection to the MQTT broker can't be established on startup and to send online statuses when establishing connection.

Discovery topics are also modified so each metric availability depends on the metric status and linuxmqtt status and to add
linux and linux2mqtt versions to device in discovery topics.

Troubleshooting is made easier by adding optional logging to directory with --logdir command line parameter and improving MQTT connection events logging

[miaucl]

Hey, this looks like quite some improvements. I admit, I also had some issues with it but nothing to annoying to motivate me to go over it. Appreciate your effort and I will surely test it but it looks already quite nice. There are just two minor details open.

• typo
• the mypy workflow seems to have a problem with the mqtt library callback version

[Endymion78]

Hi, thanks for your comments.
I fixed the typo.
I also solved the mypy workflow's error by removing types-paho-mqtt from requirements_dev.txt as it is outdated and type annotations or type stubs are included in paho-mqtt package V2.0.0 or newer (cf https://pypi.org/project/types-paho-mqtt/1.6.0.20240321/, description page).
Waiting for your feedback, I wish you a merry Christmas !

[miaucl]

Hi, thanks for your comments.

I fixed the typo.

I also solved the mypy workflow's error by removing types-paho-mqtt from requirements_dev.txt as it is outdated and type annotations or type stubs are included in paho-mqtt package V2.0.0 or newer (cf https://pypi.org/project/types-paho-mqtt/1.6.0.20240321/, description page).

Waiting for your feedback, I wish you a merry Christmas !

Thx, you too :)

Did not know they are outdated. Good to know as i will have to Patch my other libs as well.

Will test it in the following days but looks good👍

[miaucl]

Had to fix another problem first #82 and rebased your PR afterwards. It will also be >=3.12 from here on, as psutil changes quite significantly between the versions.

@Endymion78 Could you please verify again on your side as well that everything still works as you intend?

[miaucl]

Builds and runs on my test setup!

[Endymion78]

I confirm that everything is OK on my end as well.