Two Step Signup with Universal Login and OTP

We wish to implement a process for user signup where the user is prompted for a OTP after the initial sign-up form has been submitted. Ideally we’d like this to all occur in Auth0 without any redirects to another app.

Desired Steps:

  1. User is redirected from an application to the auth0 sign-up form
  2. User lands on the Auth0 sign-up form, which has a custom field added. The customer field allows the user to enter a special-identifier known by our internal systems.
  3. User submits form
    3.1. Auth0 receives form data and creates account (special-identifier is added to user_metadata)
    3.2. Auth0 Rule or Hook is triggered which collects the special-identifier from the user_metadata and then uses that to retrieve a phone number via one of our own APIs.
    3.3. Auth0 sends an OTP to the user’s phone number
  4. The user is presented with a second step where they have to enter their OTP
  5. User enters the OTP
  6. Auth0 verifies the OTP is correct and either allows or denies access
  7. If successful, the user is returned back to client (Web site or mobile device, etc)

Any assistance or ideas on how to achieve this would be appreciated , thank you!