Don't create users if they are not on the authorized users list (fixes #60)

I think the issue in #60 is a couple of things combining - first off, when a user was denied because they were not on the authorized users list, the function didn't return, and instead created the user. This pull request fixes that.

Secondly, I think there is a unique index on the email field - perhaps from a prior iteration - that is causing a dup key problem when trying to create another new user. It looks like @megamattron already fixed that.