restrict usage of e-mail address for user name
Users could certainly change their user name in their profile at https://fairchat.net/account/profile if they knew it.
We could either ask for a preferred nickname when users register or construct it in fairlogin from the e-mail address (part before @).
- fairchat oauth settings: user = preferred_username
- Keycloak mapper for the fairchat client: username / the preferred_username
Could we adapt the mapping in 1 or 2?