docs: private ScheduledExecutorService initializeHouseKeepingExecutorService()
     {
        if (config.getScheduledExecutor() == null) {
           final ThreadFactory threadFactory = Optional.ofNullable(config.getThreadFactory()).orElseGet(() -> new DefaultThreadFactory(poolName + " housekeeper", true));
           final ScheduledThreadPoolExecutor executor = new ScheduledThreadPoolExecutor(1, threadFactory, new ThreadPoolExecutor.DiscardPolicy());
           executor.setExecuteExistingDelayedTasksAfterShutdownPolicy(false);
           executor.setRemoveOnCancelPolicy(true);
           return executor;
        }
        else {
           return config.getScheduledExecutor();
        }
     }