Ahh okay tricky lil thing: if you show the settings page with a partial
change to `AuthUser` that didn't get saved, it can throw off the state
of some stuff. For example, if you don't have a password yet, then
enter a new password but leave the confirmation box blank, then you'll
correctly see "Password confirmation can't be blank", but you'll *also*
then be prompted for your "Current password", even though you don't
have one yet, because `@auth_user.uses_password?` is true now.
In this change, we extend the Settings form to use two copies of the
`AuthUser`. One is the copy with changes on it, and the other is the
"persisted" copy, which we check for parts of the UI that care about
what's actually saved, vs form state.
Emi Matchu
95c1a4f391