The ObjC UI already supports account creation for accounts that are authorised using an LDAP server. When the user is authenticated by Apache, and the remote user can be resolved using LDAP, OGo presents a Welcome page that can be used to setup the account.
This should be extended for additional authentication types supported by Apache, e.g. OAuth/OpenIDC. This may have to look for specific roles.
Maybe the welcome page should also allow/require to enter additional contact information, like phone numbers or address.