1. Added a new AttributeRouteInfo class to store all the information for
actions that are attribute routed.
2. Added a new ReflectedAttributeRouteModel class to store all the information
related to attribute routes in the ReflectedApplicationModel.
3. Refactored ReflectedControllerModel and ReflectedActionModel to use ReflectedAttributeRouteModel
instead of just the attribute route template.
4. Refactored ReflectedActionDescriptorProvider to use AttributeRouteInfo and ReflectedAttributeRouteModel
instead of just the route template.
5. Added a CombineReflectedAttributeRouteModel method in ReflectedAttributeRouteModel that handles
combining two ReflectedAttributeRouteModel instances.
6. Removed the AttributeRouteTemplate class and moved the methods for combining attribute routes to the
ReflectedAttributeRouteModel class.
7. Added unit tests for ReflectedActionModel and ReflectedControllerModel that
cover the usage of AttributeRouteInfo.
8. Added unit tests for CombineReflectedAttributeRouteModel.
This change allows a user to override a route prefix set using
[Route("...")] on the controller by providing a route template
on the action that starts with "~/" or "/". For example,
[HttpGet("~/...")] or [HttpGet("/...")]
If the user specifies a template in [Route] that starts with "~/"
or "/", we will just strip the prefix from the template and use
the remaining part of the template.
The reason to do this is that there's a reasonable extensibility
scenario where a user can implement a global prefix for routes as
a convention (using IReflectedApplicationModelConvention), and use
~/ to escape that prefix (just like we support with action-level routes).