Follow-up to #1606794: Implement new routing system
As of right now, the new routing system passes attributes from the request (such as path argument placeholders) verbatim by name. That is all well and good, but is a regression from the Drupal 7 menu router where we can up-cast, say, an id to a node object. We want to do that, but be even more cool about it.
Symfony full stack has a mechanism we can likely copy that up-converts objects based on the type hint of the parameter in the controller. That's probably the optimal way to do that. I believe that code is in the FrameworkBundle, but I haven't looked at it in detail yet.
Implement the above.
User interface changes