Stop mangling the mailing list mails

This is to be handled after the mailman migration (#59 (closed), #86 (closed))

Discussed on the 2021-03-25 devop meeting:

The mailing list configuration was changed on 2020-12-29, so all lists use @lists.archlinux.org.

At the same time, configuration differences between the lists was fixed, which means that every list now:

• Rewrites the Subject to include the list name
• Rewrites the From to avoid DMARC/spam issues

This did result in a few complains from the pacman developers, as it broke their workflow, ex pacman@c8f335ae:

author: Emil Velikov via pacman-dev pacman-dev@lists.archlinux.org

It has been suggested that we stop mangling the mails and just forward them as received (as all the big lists do), this shouldn't cause any issues as long as the original sender is probably configured.

This only user facing change, is that the users need to click Reply List or Reply All(do we have a policy on that?) instead of Reply. In the past concerns were raised, that it could be a challenge for the less tech savvy users (aur-*) to adapt to this change.