docs: public JMProgressiveManager<T, R> registerCompletedConsumer(
  			Consumer<JMProgressiveManager<T, R>> completedConsumer) {
  		Optional.ofNullable(completedConsumerList)
  				.orElseGet(() -> completedConsumerList = new ArrayList<>())
  				.add(completedConsumer);
  		return this;
  	}