counter: 1.2.0 - Service reads/writes using `JsonSerde`

counter: 1.2.0 - Service reads/writes using `JsonSerde`

- First working version of a refined topology, that reads and writes
  key and value with the `JsonSerde`.
- This topology expects and writes all data as JSON, except the key
  of the incomming messages.
- All used Serdes are directly configured in the topology.