Move webmail@spikkjeposche to webmail@bekkalokk

[h7x4]

Spikkjeposche currently hosts 4 webmail sites. We should setup hosting for new webmail clients, to remove the ones at spikkjeposche. Currently, we're aiming to set up Snappymail and Roundcube, as these seem reasonably updated. Roundcube has an existing NixOS module, while Snappymail only has a package, currently unstable.

Remember to update the wiki!

[dali99]

Don't these webmail clients do some crazy local auth things? This might be blocked on a PAM module and login support for boxes.

This might also mean they shouldn't be on bekkalokk

[h7x4]

Moved to bekkalokk