fixed bug 683, support sets the MQTT client extended options, usage: …

[hotraygroup]

…mqttAdaptor := mqtt.NewAdaptorWithAuth(...); mqttAdaptor.SetOptionsFn(func(opts *paho.ClientOptions) {opts.WillPayload = []byte("goodbye")

Solved issues and/or description of the change

...

Manual test

• OS and Version (Win/Mac/Linux):
• Adaptor(s) and/or driver(s):
  ...

Checklist

• The PR's target branch is 'hybridgroup:dev'
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes (e.g. by run make test_race)
• No linter errors exist locally (e.g. by run make fmt_check)
• I have performed a self-review of my own code

If this is a new driver or adaptor:

• I have added the name to the corresponding README.md
• I have added an example to see how to setup and use it
• I have checked or build at least my new example (e.g. by run make examples_check)

If this is a Go version update:

• go.mod to new version updated
• modules updated (go get -u -t ./...)
• CI files updated
• linter setting and linter version (if a newer one exist) updated
• linter issues fixed or suppressed by config

If this is a PR for release:

• The PR's target branch is 'hybridgroup:release'
• I have adjusted the CHANGELOG.md (or already prepared and will be merged as soon as possible)

[gen2thomas]

I'm going to set this to draft until the checklist was cleaned. For some existing comments, see old PR #889 with the same content.