Allow domain admins to create domains and verify them by TXT record

[VermiumSifell]

Summary

I would like to be able to allow all (or if possible some domain admins) to be able to create more domains, and to get them created they need to verify their ownership of the domain by a TXT record.

Motivation

This will allow my friends to create their own domains, but can also be useful for companies.

Additional context

Basicly just allow domain admins to use the create domain button, but require them to verify by TXT record.