offer experimental livekit integration

[tibroc]

This pull request introduces the option to enable livekit as media streaming backend as currently described in https://docs.bigbluebutton.org/new-features/#integration-with-livekit.

I tried to follow the patterns and structure this ansible role already uses. Please inform me where I might have it misunderstood.

It was a bit more tricky than I initially thought, because livekit-server currently generates an api-key-pair during install (see https://github.com/bigbluebutton/bigbluebutton/blob/v3.0.x-release/build/packages-template/bbb-livekit/after-install.sh#L4) that needs to be taken into account when handling the configuration files in /etc/bigbluebutton/.

[defnull]

LiveKit API secrets are just random strings, we can generate those ourselves (e.g. using {{ ('livekit' + bbb_host_seed) | hash('sha256') }}) and just replace the ones generated by livekit-server generate-keys with role-controlled values. The key name can also be any random string, as long as it starts with API. But it can also be a fixed string, no need to use secure randomness here.

If we control the key and secret, we can generate the full config file without slurping and follow the same concept as for the other config files -> merge a role-defined bbb_config_livekit_base with a user-defined bbb_config_livekit (which can be undocumented for now) and completely overwrite the /etc/bigbluebutton/livekit.yaml file.

Would you like to try that? Just make sure to to the other places where the key needs to be replaced are also all managed or fixed by the role (/etc/default/bbb-webrtc-recorder and /etc/bigbluebutton/bbb-webrtc-sfu/production.yml)

That's my only nitpick by the way, the PR looks really good :) Thanks!

[defnull]

Oh and we may need systemd overrides for livekit-server and livekit-sip to disable CPUSchedulingPolicy if bbb_container_compat is true. See bbb-html5-backend@.j2 for example

[tibroc]

@defnull I took both comments into consideration in 6c96931 and also added variable checks similar to the existing ones.

[defnull]

Looks good to me! I'll try to give it a spin later this week on our infra and the merge :)