At time of this writing, when source records are produced to their respective topic, the message key is given by default in the format
Instead, it would be useful if there was an option to configure the message key so that, for example, you could choose a different field from the change-stream document to be converted to a source record.
One particularly useful case would be to choose the "_id" of the actual collection document, if present in the
"fullDocument" "documentKey" field. This would allow the corresponding kafka topic to be partitioned on that collection's "_id" field.