Pass state into loopback oAuth callback

Question

I'm developing a polling on my site. I want only authorized users to vote. So I'am using Facebook OAuth to authenticate users.
My backend is built on node.js and using loopback framework. I'm using passport-facebook lib to perform all authorization stuff.
When user press vote up button, backend checks if user is authorized and saves vote or redirects user to login page otherwise. Everything is fine but now users have to press vote up button again after authorization. I read that there is a way to pass state as query parameter into OAuth redirect URL. And it can be done using passport.js. However loopback hides implementation and only provides static json config. At least I cannot find any mention of this in their docks and repo. So my question is how it can be handled?
Thanks for any help.