Add optional default channel to 'pub'

Description

If there is no subscriber for a topic the message gets silently dropped. I suggest to add an optional default channel that receives all those messages. The default channel can then be used in scenarios, where the complete set of topics might be unknown beforehand.
This functionality resembles the 'dead letter' pattern in messaging systems.

Environment

None

Assignee

Unassigned

Reporter

Former user

Labels

None

Approval

None

Patch

Code and Test

Priority

Major
Configure