设计+ Omniauth -如何传递额外的参数?

I have the ability in the app to load /users/auth/facebook to connect to facebook. I want to be able to know where the request came from. Whether it was from a user who is registering with facebook, or a existing user who simply wants to connect with facebook. Based on the type, the responses are very different.I have the ability in the app to load /users/au