use session.returnTo to complete connect-ensure-logged-in loop

app/controllers/auth.js

@@ -154,7 +154,7 @@ class AuthController extends SiteController {
         if (error) {
           return next(error);
         }
-        return res.redirect('/');
+        return res.redirect(req.session.returnTo || '/');
       });
     })(req, res, next);
   }