[DISCUSS] FLIP-172: Support custom transactional.id prefix in FlinkKafkaProducer

[zetaplusae]

Hi everyone,

I would like to open this discussion thread to take about the FLIP-172
<https://cwiki.apache.org/confluence/display/FLINK/FLIP-172%3A+Support+custom+transactional.id+prefix+in+FlinkKafkaProducer>,
which aims to provide a way to support specifying a custom transactional.id
in the FlinkKafkaProducer class.

I am looking forwards to your feedback and suggestions!

Thanks,
Wenhao