[Catalyst] Catalyst::Plugin::Session, Facebook, and Custom Session ids

[Jim Spath]

I'm currently using the following plugins for session management in my 
Catalyst app:

  Session
  Session::Store::Memcached
  Session::State::Cookie
  Session::DynamicExpiry

Along with the following authentication plugins:

  Authentication
  Authentication::Store::DBIC
  Authentication::Credential::Password

It all works great on my site... however, I was looking to integrate our 
app into Facebook, and to have users login to our service through Facebook.

For every request, they will be passing an parameter called fb_sig_user, 
which I should be using as a session id on our side.

I was wondering if there was a way that I could override the automatic 
creation of session ids with the Facebook id, while also continuing to 
use my current setup for onsite users?  I've looked through the docs and 
searched a bit and am unclear on this.

Thanks!
Jim