Add output kafka Idempotent

I need output to kafka for at most once . Can I create a pull request to beats output kafka as follow:

	if config.Idempotent {
		k.Producer.Idempotent = config.Idempotent
		k.Net.MaxOpenRequests = 1
		k.Producer.RequiredAcks = sarama.WaitForAll
	}

Hi @Icedroid !

We already have a Kafka output -> Configure the Kafka output | Filebeat Reference [7.x] | Elastic If this is not enough for you you can always open a Github issue or Pull Request with your addition.