Feature request or enhancement

For feature requests or enhancements, provide this information, please:

Which use case/requirement will be addressed by the proposed feature?

When using the `sink` notification channel for Debezium notifications, I am noticing the topic contains avro messages which is very odd to me for this small, low-volume topic. I assume this is because the feature is simply using the connector's key and value converter, which we have set to use avro and do not wish to change.

It would be nice if the default message type for the `sink` notification channel topic was changed to json, or at the very least have an additional configuration such that the connector could dispatch a different message format to this topic than avro.

Implementation ideas (optional)

If it can't be configurable, perhaps just change the default to be json? I believe the database history topic already uses json by default, and these are small internal topics, so I'm not sure why this topic wouldn't use json as the default as well.