Avro Payload Serializer
Thin Kotlin wrapper around Confluent's KafkaAvroSerializer configured with the Schema Registry URL taken from KafkaInfraProperties.
Serializes any Avro SpecificRecord / GenericRecord value to the Confluent wire format ([magic byte][schema-id][avro payload]) so that the resulting ByteArray can be handed to the standard ByteArraySerializer-based KafkaTemplate used by the outbox processor. Paired with AvroPayloadDeserializer on the consumer side.