Added a "specific" test schema repo and started working on testing specific insert mutations.
We can now encode and publish data based on specific Avro schemas into Kafka.
If registered in the Schema repository, it is now possible to find the needed schema based on the database name, table name, and the type of the mutation. This means that we can now generically and specifically encode and publish data sent out by MySQL's replication stream into Kafka, with versioned Avro schema support (evolution).