public VirtualHostBuilder rejectedRouteHandler(RejectedRouteHandler handler) {
        rejectedRouteHandler = requireNonNull(handler, "handler");
        return this;
    }
Sets the {@link RejectedRouteHandler} which will be invoked when an attempt to bind
an {@link HttpService} at a certain {@link Route} is rejected. If not set,
the {@link RejectedRouteHandler} set via
{@link ServerBuilder#rejectedRouteHandler(RejectedRouteHandler)} is used.
core/src/main/java/com/linecorp/armeria/server/VirtualHostBuilder.java