Signup form with phone OTP verification with custom API template

This signup form with a custom API and phone OTP verification includes:

1. An initial step that requires the full name, email and password.
2. A flow that checks if the email is available.
3. A second step that requires the phone number.
4. A flow that generates an OTP and sends it via SMS.
5. A third step that requires the verification code.
6. And last, a flow that verifies the OTP, creates the account and issues a token to automatically log the user in.