Rethinking reauth

[stuartpb]

I'm not wild about the state of reauth right now. It implies something that isn't necessarily true (for instance, if you're entering the old password after entering a new one for a password change, it's not exactly a "reauthentication", nor is it quite a reauth if you're giving your email when resetting a password a la #165.

There's also the matter of documenting the point at which you're prompted for it (#66), and the way that it's not well-designed for a post-loose-enum-like world (#149).

It's also not all that much like a word, similarly to how I ditched deauth for logout in the session enum.

All in all, I'd rather have something, probably tag-like, that naturally incorporates #66.

Come to think of it, it'll probably ride alongside #163, with there being a property for form, and then there can be a before.form and an after.form. Bam. That's the refactor. I can sleep now.

[stuartpb]

Reauth is now an emergent property of required inputs on form objects (#163). Closing this.