Support MQTT 5 protocol

[mary-ng5519]

Folks, we love your work, please help support MQTT 5 protocol,
Cheers,

[saeidakbari]

For the reference this has a very good implementation of MQTT V5.

[wind-c]

Support MQTT 5 protocol And Cluster. May refer to https://github.com/wind-c/comqtt .

[torntrousers]

Support MQTT 5 protocol And Cluster. May refer to https://github.com/wind-c/comqtt .

would be great for us users if a way could be found to have those updates in comqtt merged back here to this project

[mochi-co]

@torntrousers I will definitely be having a deeper look at @wind-c 's implementation of some of these features. I am very impressed what they have accomplished.

For mochi-co/mqtt it's important to consider the purpose of the library - which was (originally) to provide a minimalist, high performance embeddable library. We've aimed for the smallest, simplest amount of code possible in order to achieve these goals, so when it comes to features like clustering, there's a lot to consider.

I do think it would be nice to add these features, but they need to be balanced against maintainability and performance - and there's a few areas nin the existing codebase we need to improve first (like #101) :)

[torntrousers]

For sure, all good for me and thats why we use your project.

[mochi-co]

Resolved in v2.0.0