Provide a web archive of team emails

Many teams would like to use the new team+slug@tracker.debian.org email to discuss between team members but their main issue is that those mails are not archived publicly.

We should consider providing this service. Maybe we can implement it on top of Hyperkitty which is a Django application doing precisely this for the Mailman 3 mailing list manager.

See https://gitlab.com/mailman/hyperkitty and https://hyperkitty.readthedocs.io/en/latest/