A way to use a custom subclass of PathView

[way-dave]

Right now, PathView is an internal implementation detail. However, have some use-cases that would benefit from a blessed way to use our own PathView subclass.

This is analogous to the existing ability to use a custom Router subclass.

It would then be very useful to be able to customize the PathView._find_operation, allowing custom dispatch logic to be implemented.

Our specific use-case is header-based API versioning, which would require dispatch based on a HTTP header as well as method and path.

[way-dave]

(I'm aware I've been making a bunch of posts here recently, so thanks for your responses so far. I'm very happy to contribute PRs for anything you consider worthy of inclusion, FWIW. ❤️ )

[vitalik]

@way-dave well... you can make you class inherited from Router and then overwite the add_api_operation method

class MyPathView(PathView):
       ...


class MyRouter(Router):
     def add_api_operation(...):
         ...
        if path not in self.path_operations:
            path_view = MyPathView()
            self.path_operations[path] = path_view
        else:
            ...
        ...

router = MyRouter()

@router.post(..