Well you can, if you have an account, signed up with normal email and password, and while logged in, try to log in again with oauth, you merge the accounts.
You are saying, is that to do the catch info I need auth0?
Also here’s the documentation for it:
Signing up when logged in: When a user already logged in with their email and password chooses to link their account with an OAuth provider, their existing account gets updated with the new authentication credentials. This means no new user account is created. After completing this linking process, the user has the flexibility to log in either with their email and password or through the OAuth flow.