Add a way to initialize self-registration directly

[isoroka-plana]

Is your feature request related to a problem? Please describe.

We have a feature in the app that serves as enrollment for the users where they first have to go through a KYC process. As a result of this process, we can tell they need to create an account first. So we need to skip the login screen and lead the users directly into the sign-up screen with self-login.

Describe the solution you would prefer

A method or a parameter (similar to Auth0's screen_hint) that allows doing sign-in via sign-up. Calling .signUp() would start the authorization process and redirect to the registration screen, upon sign up the user would be redirected back to the app where we could call .signIn() to finalize the sign-in process and be able to obtain the token.

Additional context