Member predicate Routing :: RouteSetup :: Base :: getRelativePath
Gets a path prefix to be matched against the path of incoming requests.
If the prefix matches, the request is dispatched to the first child, with a modified path
where the matched prefix has been removed. For example, if the prefix is /foo and the incoming
request has path /foo/bar, a request with path /bar is dispatched to the first child.
If the prefix does not match, the request is passed on to the continuation.