Add request.url_for method

[RobertoPrevato]

🚀 Feature Request

Add a request.url_for method (including helper for Jinja2), supporting an optional name?

Maybe:

def url_for(path: str, *, name: str | None = None):
    ...

Like in Starlette (ref):

Mount("/users", name="users", routes=[
        Route("/", user, name="user_list"),
        Route("/{username}", user, name="user_detail")
    ])

[mavwolverine]

We also need Mount support for subrouting.