Migrating an application to Phoenix running on Firebase Keep Firebase or migrate to Postgres?

Hello,

I have an application running on Vercel with Firebase (for user application data but also for Authentication on Firebase) and I am migrating this to Elixir/Phoenix/Liveview.

I am struggling with migrating the Authentication part into Postgresql. It is very easy (social logins etc) in Firebase but I can’t seem to find out correctly how to migrate the authentication to Postgres without having the users to make a new login.

My question is, would you either:

1/ migrate my current users who use social logins (google/github/microsoft) to postgres if possible?

or

2/ keep using firebase as the main database and authentication system in my Phoenix application (if this even possible?)

I would like to know what your choice would be,

Thanks for your help!