code: protected PathMapped<Service<I, O>> findService(PathMappingContext mappingCtx) {
          assert router != null;
          return router.find(mappingCtx);
      }
docs: Finds the {@link Service} whose {@link PathMapping} matches the {@code path}.
  
  @param mappingCtx a context to find the {@link Service}.
  
  @return the {@link Service} wrapped by {@link PathMapped} if there's a match.
  {@link PathMapped#empty()} if there's no match.