ksqlDB KT with another stateless operation like concatenation, changing case

Similar to https://kafka-tutorials.confluent.io/transform-a-stream-of-events/ksql.html

Maybe add a new one that shows things like concatenation, changing case, dropping fields, etc etc

The referenced transform-a-stream-of-events ksqlDB tutorial is the only entry point named; start by reviewing its structure and the repository's existing tutorial conventions. Done means adding a comparable tutorial that demonstrates stateless operations such as concatenation, changing case, and dropping fields.

Written by the indexing model from the issue text.