Add metadata to Dead lettered Messages

[gabo1208]

Problem
Messages that fail to be delivered are Dead lettered without any modification, leaving the system/user with no easy way to know why they ended up there. A knative recommendation for this is to add some extra fields in this case that adds that missing info:
https://knative.dev/docs/eventing/event-delivery/#configuring-channel-event-delivery

Persona:
Users

Exit Criteria
Deadlettered messages now have metadata on why they ended up in the DLQ

• Implement DLQ metadata for the Broker Delivery failure #1163
• Implement DLQ metadata for the Source

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[andrewwebber]

Is there any update on this other than it is scheduled for the "next" release?

[github-actions]

This issue is stale because it has been open for 90 days with no
activity. It will automatically close after 30 more days of
inactivity. Reopen the issue with /reopen. Mark the issue as
fresh by adding the comment /remove-lifecycle stale.

[gabo1208]

Yes @andrewwebber We are finally getting this into Knative RabbitMQ!

We had some issues since is not well supported yet in RabbitMQ but we ended up implementing a solution here meanwhile!