[FEAT] Confirm new SuperUser workflow

[tsdobbs]

Basic Users are implicitly confirmed when they confirm an artpiece via email. SuperUsers are created through a different process, so a similar email workflow should be triggered for when a new SuperUser is created - they should get an email asking them to confirm that they signed up (or were signed up) as a SuperUser. This will catch typos on user creation - if the email was wrong, then the SuperUser simply never gets confirmed, and the record can be ignored.