We have two social sign-in methods, both have an e-mail trait(imagine Facebook, Github). If a user logs in with both social sign-ins using the same e-mail, we want to treat those accounts as distinct accounts instead of throwing an error. 1. The first idea is to use a custom schema and treat the login identifier of the user as username. Would this work? 2. In case we want to change the schema for the identities, is there a way to migrate all identities to the new schema without any user losing access to their account / their id being changed?