Support delaying PUBACKs in libmosquitto API

[Damiano Albani]

In the situation where a libmosquitto-based client subscribes to a topic with QoS=1, it would be useful to be able to delay the PUBACKs that it sends back.
Instead of the current automatic behavior, the API would provide a callback to manually send a PUBACK for a specific message.
The idea being that it confirms that the message has been correctly processed locally and is ready to be acknowledged to the broker.

The feature was already mentioned in a message from the mailing-list a year ago: https://lists.launchpad.net/mosquitto-users/msg00024.html

And I see that the MQTT.js implementation supports such a feature: https://github.com/adamvr/MQTT.js/pull/77

[Roger Light (roger.light)]

This is a good idea, I'll look into it for version 1.3.

[Roger Light (roger.light)]

Hi there,

I'm migrating bugs to Eclipse, the new url for this bug is:

https://bugs.eclipse.org/bugs/show_bug.cgi?id=452930