Hello.

My oauth2 provider handles multiple idP(s), and I can specify which one to use by setting "selected_idp" parameter to authorize URL

http://www.cilogon.org/oidc

I see that I can add arbitrary parameters to authorize URL by overriding authorizationParams() function, but this function doesn't allow accessing user request parameter.

Can you add an additional option parameter to authenticate() so that I could do something like

router.get('/signin', function(req, res, next) {
    passport.authenticate('oauth2', {
        authorize_params: function() {
            return {selected_idp: req.query.idp}
        }
    })(req, res, next);
});

??