Add PublishCorrelated Request/Outgoing event to associate a Publish…

[mneumann]

… message with an external id

This simplifies associating a published message with the pkgid that it
got assigned, without having to resort to event ordering.

[mneumann]

Same as bytebeamio#291. Not sure if they will accept that PR. Our mqtt_client depends on this functionaliy.

[mneumann]

@rina23q Can you create a separate branch from that? I would not like to merge that into the main branch. For as long as upstream rumqtt does not accept our changes, it's better to depend on a rumqtt fork maintained by thin-edge organization (and not a repo maintained by myself!).

[mneumann]

@makr11st @didier-wenzek please review if you have time. this is just the functionality we need for our mqtt_client library.

[makr11st]

It looks good to me, but I'm still struggling to see where do we need it in our client?

[mneumann]

@makr11st https://github.com/thin-edge/thin-edge.io/blob/main/common/mqtt_client/src/lib.rs#L189
If we can get rid of publish_with_ack, we can get rid of this!

[makr11st]

@makr11st https://github.com/thin-edge/thin-edge.io/blob/main/common/mqtt_client/src/lib.rs#L189
If we can get rid of publish_with_ack, we can get rid of this!

It is only used in an example, no where else:
common/mqtt_client/examples/publish_test.rs

Do we really need this feature?