MQTT v5.0 support

[boneskull]

Add MQTT v5.0 support to this client.

I'll enumerate what those changes are when I figure out what they are. I plan to begin this work in earnest after I've done something about #138, and I can start #138 after next week.

References, prior art, etc:

• MQTT v5.0 Committee Specification 01
• Somebody's overview of the changes
• v5.0 conforming broker written in Swift
• Trivia
• Ian Craggs' post on the topic to the paho-dev list

[ashchurko]

Whenever you will be ready to start 5.0 protocol integration we have broker ready for play with. And we need 5.0 features in jscript client. The most valuable in my opinion are: commands(response topics), message expiration interval and will delay interval.

[manifest]

Is there any progress on this one? There are currently a bunch of brokers that have already implemented v5 support.

[ashchurko]

mqtt.js already contain 5.0 protocol support

[damouse]

Any progress?

[arreumb]

Is support for MQTT v5.0 for paho javascript client abandoned ?

[davidhmays]

Can we please know if MQTT v5.0 is supported in Paho.MQTT.Javascript?

[joed74]

I added basic MQTT v5.0 support to be able to read userProperties: https://github.com/joed74/paho.mqtt.javascript