Kafka test with specialized serializer and deserializer

[singhbaljit]

KafkaConsumerHelper#convertProtobufToJson and KafkaProducerHelper#buildProtoMessage assume that we're using ByteArrayDeserializer and ByteArraySerializer. They expect the ConsumerRecord#value() to be a byte[] or return a byte[]. This is problematic when using special SerDes that handle the low level parsing/serialization; for example, the SerDes from https://github.com/awslabs/aws-glue-schema-registry or Confluent's SerDes for their Schema Registry. These libraries handle the POJOs directly, i.e. ConsumerRecord#value() will be of type MessageOrBuilder, and no further parsing (via Reflection) will be needed. There should be a property that allows overriding the default behavior so KafkaConsumerHelper and KafkaProducerHelper just accept/return POJO of the wire type instead of byte[].