private ScheduledThreadPoolExecutor newBlockingTaskExecutor() {
        final ScheduledThreadPoolExecutor blockingTaskExecutor = new ScheduledThreadPoolExecutor(
                getMaxThreads(),
                ThreadFactories.newThreadFactory("armeria-dropwizard-blocking-tasks", true));
        blockingTaskExecutor.setKeepAliveTime(60, TimeUnit.SECONDS);
        blockingTaskExecutor.allowCoreThreadTimeOut(true);
        return blockingTaskExecutor;
    }
a helper method to facilitate the signature change in {@link AbstractServerFactory} in release 2.1, where
the 5th {@link AdminEnvironment} param is added.
dropwizard2/src/main/java/com/linecorp/armeria/dropwizard/ArmeriaServerFactory.java