I can see `RoutingHttpHandler` is a combination of...

# http4k

[xenomachina]

I can see RoutingHttpHandler is a combination of a Router and HttpHandler, but exactly what that means isn't entirely clear. When does match return null? What precisely does it mean for an HttpHandler to not be able to service a Request? An HttpHandler is a function that takes a Request, so if I gave it one it "can't service", what would happen?