[keycloak-dev] Customizing usernames

Hi all, I'm looking for a way to customize the unique identifiers used by Keycloak in its internal user database, to avoid possible email or username clashes. For example, I would like to be able to change the username of someone logging in through github to "login(a)github.com", so that if someone has the same login in the CERN LDAP the user is not offered the possibility to merge the accounts. Our problems come from the fact that we allow people to change their mail addresses, and also to use external non-CERN addresses as their email, so we cannot rely on email much. We would also like to avoid people to merge accounts at all as we think this might be confusing for users on some occasions, and generate support tickets for us. Is there a supported way to do this, or would we need to code something ourselves? If we need to code something, should we write a plugin of some kind (e.g. custom mappers) or would we need to modify directly the code that manages the login from the identity provider? In case someone else requested something similar, we might make our development available. Thanks, Paolo Tedesco