Allow consuming/producing Kafka tombstones when using Kafka PubSub with Avro

[GregerTomas]

Currently, consuming/producing tombstones Kafka messages is not supported when using Avro schema validation. Null values should be treated specially and not be validated by a schema.

See also https://discord.com/channels/778680217417809931/901141467840524289/1276090536976973845

[passuied]

@GregerTomas in our experience, tombstone events are supported for Avro as well... It was a bug 6+ months ago but has been addressed...
Could you provide more details about your issue?

[passuied]

@GregerTomas as mentioned on discord, we were able to reproduce the issue but only on the produce. I have a fix and will submit a PR shortly

[GregerTomas]

@passuied Yes, sounds good. I was able to recieve tombstones which were sent by non-Dapr producers (aka custom Dapr header were not present). When I sent a tombstone using Dapr, I recieved mentioned error.

[passuied]

@GregerTomas this should be resolved. Please confirm

[GregerTomas]

@GregerTomas this should be resolved. Please confirm

confirmed