OMEMO support for XMPP backend

[tuxinflux]

I am...

• Suggesting a new feature

I am running...

• Errbot version: 6.1.8
• OS version: Ubuntu 20.04.2 LTS
• Python version: 3.8.2
• Using a virtual environment: yes

Issue description

It would be really nice if the XMPP backend could support OMEMO (XEP-0384)

Additional information

Since the XMPP backend is based on slixmpp there might be a good chance that the library slixmpp-omemo could fill this gap. To my unterstanding, slixmpp-omemo seems to be a plugin for slixmpp and only separated as an plugin library due to licences issues.

[nzlosh]

Thanks for taking the time to raise this feature request. At this point, I'd suggest you fork the xmpp backend and implement the feature yourself if you require it.

Errbot development resources are thin and it would be very hard to convince anyone to work on implementing an experimental XMPP feature with the uncertainty of it becoming officially supported as well as using a library that self proclaims its unworthiness for the cryptographic use case OMEMO requires.

If XEP-0384 becomes an official standard, we may see a more dependable module developed and officially integrated into slixmpp by default, in which case errbot will most definitely support it.