Resolve enum refs in URL schemas

[piercefreeman]

Users sometimes want to set up a controller that will respond to multiple URL paths (/abc/item_details and def/item_details for instance). This PR adds support for including enum definitions within URL paths. We will parse these as expected at call-time and include the enum typehints within the links controller.

class ItemType(StrEnum):
    A = "A"
    B = "B"

class MyController(ControllerBase):
    url = "/{item_type}/{item_id}"