Remove registration email from DB

[RomanistHere]

For those who don't want to be identified even if we somehow leak the data from DB we can remove email from email field and change it to any string user wants.

However, we need either to keep all the emails (just as a list) in a separate DB, not connected to to users, so we prevent multiple registrations from the same email or make it cost something like 20$ - 50$ in crypto to completely wipe it out.