This is done with slight adaptations from the official guide at
https://jitsi.github.io/handbook/docs/devops-guide/secure-domain
Amongst other changes, we rely on Prosody's configuration parser only overwriting the parts of a VirtualHost that are explicitly specified in "later appearing" (lexicographically speaking) files.
This allows us to let Jitsi manage the main config file and adding the few customisations on top of it.
We also use the Plaintext authenticator as this is enough atm and is the easiest to manage in an idempotent fashion; support for other authentication mechanisms is possible, see Prosody's documentation for that.
Jitsi's repositories have rotated keys, this removes the previous key if
necessary and ensures the new key is present.
Can't be merged until following lands:
https://code.ungleich.ch/ungleich-public/cdist/-/merge_requests/994
since we rely on `--use-deprecated-apt-key` and the improvements in the type to
modify the keyring in a reliable fashion.
This also updates the exporter to version 1.1.5 released on April 25th 2021.
