Best practices for creating users in backend DB on new registrations with Auth0

[dan.woda]

@valb

Con: we need an additional trip to Auth0 Management API and potentially (read: hopefully) can reach rate limits if we have too many concurrent new users (e.g. over 1000 per minute).

One question we have is why you would need a call to the management API at all. You should be able to use the ID token returned from the initial authentication to create a user in your DB.