https://cwiki.apache.org/confluence/display/KAFKA/KIP-202+Move+merge%28%29+from+StreamsBuilder+to+KStream
KIP-202 Move merge() from StreamsBuilder to KStream - Apache Kafka - Apache Software Foundation
https://kafka.apache.org/24/javadoc/org/apache/kafka/streams/StreamsBuilder.html
StreamsBuilder (kafka 2.4.1 API)
kafkaapi