Add MUC and OMEMO support

[ichthyx]

This PR add support for MUC (groupchat) and OMEMO (bot to user) and MUC OMEMO.

Currently private discussion (from user to bot) doesn't support omemo, we should implement omemo support in message() function. Not sure if I have the time for do it now, maybe later.

It add a new dependency which is slixmpp-omemo. Most of the code come from the slixmpp example : https://codeberg.org/poezio/slixmpp-omemo/src/branch/main/examples/echo_client.py

I used black to format code, it seems to have mess a lot of code, if you can suggest your way of formatting.

[jelmer]

Thanks; looks good overall. I've left some minor comments.

Please take a look at the test failures.

Also, would it be possible to submit the formatting changes separately, or drop them? As-is they make the PR quite hard to read & review.

[ichthyx]

Also, would it be possible to submit the formatting changes separately, or drop them?

I don't know how to do that, I tried to migrate to official pep8 formatting standard, not sure how to handle this.

Please take a look at the test failures.

Error are type checking. I don't know and never used mypy, so it's likely to take me some time.

Apart from that, most of the problems have been solved.

[jelmer]

Ack, let me see if I can cherry-pick some of your changes.

[jelmer]

I've create a new PR with your changes and without the formatting in #44 - I originally tried to update your branch, but accidentally closed the PR in the process.

Let's continue the conversation on #44