VirtualHostBuilder addRouteDecoratingService(RouteDecoratingService routeDecoratingService) {
        if (Flags.useLegacyRouteDecoratorOrdering()) {
            // The first inserted decorator is applied first.
            routeDecoratingServices.addLast(routeDecoratingService);
        } else {
            // The last inserted decorator is applied first.
            routeDecoratingServices.addFirst(routeDecoratingService);
        }
        return this;
    }
Returns a new instance of {@link VirtualHostAnnotatedServiceBindingBuilder} to build
an annotated service fluently.
core/src/main/java/com/linecorp/armeria/server/VirtualHostBuilder.java