Automatically add Roundcube PGP keys into PGP keys on MIAB, and ability to auto-publish keys on MIAB to the WKD

[eris-webserv]

Title. My users like OpenPGP and having the ability to automatically publish to the WKD would be very nice to have.

[ddavness]

FWIW I might need to rework a bit of the PGP/WKD feature anyway, so that we can have something like the GnuPG WKS Server running there (which should accomplish what you want to do).

For now, the obvious "workaround" is to do this manually (which understandably may not be scalable to do)