static GracefulShutdownSupport create(Duration quietPeriod, Executor blockingTaskExecutor, Ticker ticker) {
        return new DefaultGracefulShutdownSupport(quietPeriod, blockingTaskExecutor, ticker);
    }
Keeps track of pending requests to allow shutdown to happen after a fixed quiet period passes
after the last pending request.
core/src/main/java/com/linecorp/armeria/server/GracefulShutdownSupport.java