Configure Debezium outbox event router SMT to implement the transactional outbox pattern for reliable event publishing

Steps

1. Create an outbox table with columns: id (UUID PK), aggregatetype, aggregateid, type, payload (JSON), and timestamp; insert rows within the same database transaction as the domain change
2. Configure the outbox SMT: transforms=outbox,transforms.outbox.type=io.debezium.transforms.outbox.EventRouter
3. Set transforms.outbox.table.field.event.id=id, transforms.outbox.table.field.event.key=aggregateid, transforms.outbox.table.field.event.payload=payload, transforms.outbox.route.by.field=aggregatetype
4. Set transforms.outbox.table.expand.json.payload=true to deserialize the payload column as a structured JSON object rather than a raw string in the Kafka record value
5. Optionally set transforms.outbox.route.topic.replacement to a topic naming template; the aggregatetype value becomes the Kafka topic name by default