Add option to pass custom user uuid on sign up

I'd love to have the ability to pass a custom uuid for new users.

Background:
I have a react native application where creating an account is optional.
New app users get a custom (local) uuid on initial app start. This is generated in the app.
Ideally they would keep that id if they decide to create an account at a later time because it's easier to trace users (IAP, analytics) if the user ids remain the same through the entire lifetime.

The interface could look like this for sign up with otp:



Thanks!