When using FlutterfireUI, I would like to use a callback that is executed only when a user registers

Question

I am building an app using Flutterfire_UI's SignInScreen and other features.

I would like to generate a user document for each user in the users collection of firestore upon user registration.

I would like to use a callback that is executed only when a user registers, but I don't know how to do it.

I can set up a callback for every sign-in by setting up an AuthStateChangeAction callback, but that means I have to check each time whether it is the first time or not, so if there is a smarter way, please let me know.

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