Several refactoring and clean ups in the Kafka producers for generic and specific Avro encoding.
Cleaner separation between Kafka topics and Avro Subjects.
Added helper calls and a util to register Avro schemas in the repository.
Kafka generic consumer test passes again now that the topic names are in centralized utils and are being used correctly.
Renamed function used to get Avro Schema's Subject in the KafkaMutationAvroConsumer to be more reflective.