Sending invites to facebook friends

[florian...@gmail.com]

Hi,

I am trying to integrate Facebook into an existing application. I want to do two things:
- Add the ability to pull user data from facebook and fill it into a user registration form for an account on the website.
- Give users the ability to invite other facebook friends to Facebook Using a single dialog on the app itself, so no redirect to Facebook. For this, I realize one-time authentication is required. This is fine, but I want to store this auth somewhere so it is remembered on subsequent visits. Would an access_token column in the user model be smart in this case, or would you guys suggest writing it to a cookie on the user's local system?
This is on Ruby 2.0 and Rails 3.2.1. Could anyone here give me a few pointers?

Thanks a lot in advance,
Florian