title: Kafka stream append to JSON as event enrichment
body: <p>I have a producer that writes a json file to the topic to be read by a kafka consumer stream. Its simple key-value pair.
  I want to stream the topic and enrich the event by adding/concatenating more JSON key-value rows and publish to another topic.
  None of the values or keys have anything in common by the way.
  I am probably overthinking this, but how would I get around this logic?</p>