Breaking API Changes Under Consideration

• Avro serdes should allow producing an consuming of null values: https://github.com/confluentinc/confluent-kafka-dotnet/pull/1344
• ConsumeException is confusing to users in the case of Schema Registry / serialization problems. We should consider not wrapping this type of exception. Or maybe we extend ConsumeException (but that is possibly overly complex).