Only perform verification or update existing user

[yousifa]

Is there a way to update an existing user?

For example: A user is already signed in, but now wants to auth using social auth (in my case, apple id). Instead of creating a new account when they authenticate, I want to update their existing account if they are already authenticated with a token.

If this is not possible out of the box, is how can I call only the verification process and decide whether to create an account / update an account on my own (and receive the user's new data)?