feat: add a metadata system to specialize controllers and routes

[francescovallone]

The metadata system can be used to specialize controllers and routes. For example, suppose one route within a controller does not need to be authenticated, while the others do. In that case, an isPublic metadata can be defined and applied to the route or controller. This way hooks can check whether the route or controller contains that metadata and behave differently.

[francescovallone]

The metadata can be used to prevent the exposure of both the controller and route instance in the request context