Structured userData in JMX Notifications

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

Programatic consumption of notifications from io.debezium.pipeline.notification.channels.jmx.JmxNotificationChannel where the attributes of the underlying io.debezium.pipeline.notification.Notification are used.

Implementation ideas (optional)

Today the notification userData is passed as the return value of Notification#toString. This makes it hard for notification consumers to read properties such as type, aggregateType and additionalData from the original notification, since the only way to do it would be to parse the string.

See https://github.com/debezium/debezium/blob/394a9e32d88eee553410e1a2c9d05504e396b9d9/debezium-core/src/main/java/io/debezium/pipeline/notification/channels/jmx/JmxNotificationChannel.java#L70

My suggestion is to convert the .debezium.pipeline.notification.Notification into javax.management.openmbean.CompositeData and thereby expose it in a structured (yet MXBean compliant) way.