Refactor jolokia fields

[ChrsMark]

This is a draft PR that possibly could resolve_ #13316

[elasticmachine]

Pinging @elastic/integrations-platforms (Team:Platforms)

[exekias]

This would be a breaking change so we would need to put it behind a flag, what do you think about it @jsoriano ?

[jsoriano]

@ChrsMark thanks for starting to work on this! The initial approach looks good, but I think we need to do some more things to have a complete support.

As said by @exekias, we would need to put this feature behind a flag, both modes are going to need to coexist for a time, maybe forever (namespacing and explicit mapping is useful in light modules, think on the light metricsets of the kafka module, or the tomcat one). Having a flag will also allow to merge this earlier, and incrementally improve the support on this new mode. In some major version we can then decide to use the new mode by default.

[jsoriano]

It would be nice to support all types Jolokia knows how to serialize, and we will have to check to what types they are converted when Unmarshalling. We will need a good set of test cases for this.
You can find the list of supported types here: https://jolokia.org/reference/html/protocol.html#serialization-response

Take also a look to the list operation, that allows to obtain information about the MBean attributes, including its type and description. Knowing the type we could do a proper handling without depending on how the value is converted to JSON and Unmarshalled. (With the description we could also provide some tool to autogenerate the documentation on light modules, but this is another story).

[mergify]

This pull request does not have a backport label. Could you fix it @ChrsMark? 🙏
To fixup this pull request, you need to add the backport labels for the needed
branches, such as:

• backport-v./d./d./d is the label to automatically backport to the 7./d branch. /d is the digit

NOTE: backport-skip has been added to this pull request.

[mergify]

This pull request is now in conflicts. Could you fix it? 🙏
To fixup this pull request, you can check out it locally. See documentation: https://help.github.com/articles/checking-out-pull-requests-locally/

git fetch upstream
git checkout -b jolokia_fields_refactor upstream/jolokia_fields_refactor
git merge upstream/master
git push upstream jolokia_fields_refactor

[jlind23]

@ChrsMark - Closing this one as there were no activity for a while