public ServerBuilder rejectedRouteHandler(RejectedRouteHandler handler) {
        virtualHostTemplate.rejectedRouteHandler(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. By default, the duplicate
routes are logged at WARN level.
core/src/main/java/com/linecorp/armeria/server/ServerBuilder.java