Using email or nickname to log in using authlogic and Rails 3

This is a continuation of my first authlogic/Rails 3 post.

Authlogic users have both "login" and "email" properties by default. I wanted to allow users to log in via their email address or nickname. I tackled this in two steps. First, switch to logging in using the "email" property. Second, create a "nickname" property, and allow users to log in with either one. (Yes, I actually wanted to call