public T build(Function<? super HttpService, ? extends HttpService> decorator) {
        requireNonNull(decorator, "decorator");
        buildRouteList().forEach(
                route -> contextPaths().forEach(contextPath -> builder.addRouteDecoratingService(
                        new RouteDecoratingService(route, contextPath, decorator))));
        return builder;
    }
Sets the {@code decorator} and returns the context path service builder.

@param decorator the {@link Function} that decorates {@link HttpService}
core/src/main/java/com/linecorp/armeria/server/AbstractContextPathDecoratingBindingBuilder.java