Register user and authenticate request on server using facebook

I have an app that uses ember simple-auth with torii and devise extensions. My backend is on rails with devise to protect ressources. (BTW, I am a rails noob)

My goal is that I want users to be able to register/login with facebook, but I also need to authenticate requests made to my backend. (e.g. A user can only access his account info)

If I take each authenticators by itself, it works fine. For example, I can authenticate a user through facebook. And I can register and sign in on my rails server. However, I want the registration to happen through facebook( No forms to fill for the user)

The questions I have are: - What information should I persist on my server so that I can identify a facebook authenticated user and authorize him to access ressources? - Is there a more straight forward way to do it ? - Does it even make sense to have 2 authentication processes ?