okta registration inline hook - prevent duplication

The Inline Hook post content to the /verifyRegistration endpoint.

If a user is created via self-service registration, this hook will be used.

If email is matched to a current Okta user, an error is returned to user indicating the user exists and registration is blocked.

If phone number is matched to a current Okta user, an error is returned to user indicating phone number is already registered for a user and registration is blocked.

If no matching user is found, registration is completed and user is logged into the application.