Is it possible to implement phone authorization using a third-party SMS provider?

Hello community ! Please help me understand if it is possible to implement this flow:

FF works with Firebase.

1) new user enter his phone number

2) FF send OTP SMS through my local provider

3) user enter OTP from this SMS

4) this user added in Firebase's "users" collection

5) FF gives me his standart functionality of using object "Authenticated User"

Is it real ?

I've done steps 1-3, but I can’t figure out how to add such a user to Firebase and link it to "Authenticated User".