Custom kafka single message transformer used by debezium to "flatten" the message structure

Usage:

Add to debezium config the following:

# Transforms
debezium.transforms=unwrap,collapse
debezium.transforms.unwrap.type=io.debezium.transforms.ExtractNewRecordState
debezium.transforms.collapse.type=server.CollapseCassandraCells

unwarp drops standard "before" part and keeps only "after" one. collapse transforms the json from looking like:

{
    "user_id": {
        "value": "user1",
        "deletion_ts": null,
        "set": true
    }, ...
}

to something more usable like:

{
    "user_id": "user1",
    ...
}