Movie sessions function out of server.js

[ko-karol]

Seeing as we're requiring a bunch of modules already and just calling functions in server.js, it might be better to also do the same with the sessions function.

function sessions(req, res, next) {
    const sid = req.signedCookies.sid; //undefined if there is not a sid
    const session = getSession(sid); //undefined if there is no session
    if (session) {
        const expiry = new Date(session.expires_at);
        const today = new Date();
        if (expiry < today) {
            removeSession(sid);
            res.clearCookie('sid');
        } else {
            req.session = session;
        }
    }
    next();
}