Apache Camel persist failed messages to Postgresql dead letter table

Question

I'm using Apache Camel to build integrations, and I want to persist failed messages so I can build the UI and allow user to redeliver / reprocess them when they decide it's time to do it.

I have a working example on how to send a failed messages to the dead letter queue (e.g. Kafka), but I'm struggling to persist them to the PostgreSQL.

Kafka example:

- routeConfiguration:
    errorHandler:
      id: errorHandler-d669
      deadLetterChannel:
        deadLetterUri: kafka:failed-messages?brokers=kafka:9092
        redeliveryPolicy:
          maximumRedeliveries: 2
          redeliveryDelay: '1000'
          backOffMultiplier: 2
          useExponentialBackOff: true
          retryAttemptedLogLevel: WARN
          id: redeliveryPolicy-215f
        level: ERROR
        id: deadLetterChannel-6c51
    id: deadletter-kafka

This will send entire Exchange message to the Kafka topic named failed-messages and produce entry in the queue similar to this:

Exchange[Id: 7384875AE37D9B7-0000000000000004, ExchangePattern: InOnly, Properties: {CamelMessageHistory=[DefaultMessageHistory[routeId=route-5893, node=to-d19e]], CamelToEndpoint=log://deadletter-logger?level=WARN&showAll=true}, Headers: {CamelMessageTimestamp=1703585126556, Custom-Header-1=[B@1509b733, Custom-Header-2=[B@d9561f8, kafka.HEADERS=RecordHeaders(headers = [RecordHeader(key = Custom-Header-1, value = [79, 110, 101]), RecordHeader(key = Custom-Header-2, value = [84, 119, 111])], isReadOnly = false), kafka.OFFSET=11815, kafka.PARTITION=0, kafka.TIMESTAMP=1703585126556, kafka.TOPIC=failed-messages}, BodyType: String, Body: It's me, Mario, on 2023-12-26T10:05:23 - Enriched]

My problem is that when doing the same to the PostgreSQL table, I need to specify expression from which to read the failed message and I'm unable to do so:

- routeConfiguration:
    errorHandler:
      id: errorHandler-d679
      deadLetterChannel:
        deadLetterUri: >-
          sql:insert into camel_deadletter (exchange_message) values (:#${SOMETHING})
        redeliveryPolicy:
          maximumRedeliveries: 2
          redeliveryDelay: '1000'
          backOffMultiplier: 2
          useExponentialBackOff: true
          retryAttemptedLogLevel: WARN
          id: redeliveryPolicy-216f
        level: ERROR
        id: deadLetterChannel-6b51
    id: deadletter-sql

I need to specify SOMETHING in above's example, but I'm not sure what to put there.