Add support for MQTT 5 message expiry interval property

[dimabarbul]

Message expiry interval property in MQTT 5 allows specifying that a message is valid for limited period of time. This allows a message broker to discard messages when the interval is up, and clients will not receive (and process) messages that are expired.

An example of such message can be live message to device that requires response. Processing such message after the timeout is unnecessary (and sometimes not desirable).

It would be nice to have special mqtt.message-expiry-interval (or, probably, something shorter) header that contains/sets message expiry interval property (for source and target mappings).

[thjaeckle]

Sounds good, but only makes sense when producing messages, so for targets.

Or can it be of use when read out from a consumed message?

[dimabarbul]

Good question. I don't have good answer though :-(

I noticed that, for example, mosquitto provides expiry interval in consumed messages properties. So I suppose that it might make sense for some scenarios.

I can't imagine such scenario, tbh, but I don't have a reason to say that it should not be available for sources.