Either
* Redirect openid login requests to session controller
* Move openid login into Module for reuse by all controllers

On complete (from OpenID provider)
* Login if OpenID exists; and redirect to where the user expects to go
* Create User + UserOpenid otherwise
  * if !User.valid? redirect to user#edit to complete registration; on save, redirect to where user expects to go
  * else redirect to wherever user expects to go