scambra/devise_invitable — pull request #395 by ginter (2013-10-17 17:23:07+00:00)
Title: values for the invite key hash can be anything that responds to the === operator

This allows for any additional fields you wish to be validated upon invite. I also removed the nil check since the only time this method is called is if validate_on_invite is false and in that case specifying an attribute as an invite key only to allow it to be nil seems pointless unless I'm missing something.