[java-generator] Add native support for date-time fields

[andreaTP]

Description

This PR adds native support for date-time format of fields of type string.
Please note that this is a breaking change, we should at least bump the minor version to introduce it.

date-time native parsing is very useful, especially in the standard Conditions in the Status stanza (e.g. https://maelvls.dev/kubernetes-conditions/ lastTransitionTime).

Type of change

• Bug fix (non-breaking change which fixes an issue)
• Feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change
• Chore (non-breaking change which doesn't affect codebase;
  test, version modification, documentation, etc.)

Checklist

• Code contributed by me aligns with current project license: Apache 2.0
• I Added CHANGELOG entry regarding this change
• I have implemented unit tests to cover my changes
• I have added/updated the javadocs and other documentation accordingly
• No new bugs, code smells, etc. in SonarCloud report
• I tested my code in Kubernetes
• I tested my code in OpenShift

[andreaTP]

cc. @fabiobrz might be interested in reviewing 🙂

[fabiobrz]

Thanks for this PR @andreaTP ! I dropped a couple of questions and suggestions. Let me know what you think.

[andreaTP]

thanks for the review @fabiobrz ! Ready for the next round!

[fabiobrz]

Thanks for addressing my comments, @andreaTP.
Changes LGTM, approving. BTW - Feel free to squash your last commit ("review").

[andreaTP]

Squashed and ready 👍

[sonarqubecloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
1 Code Smell

80.0% Coverage
0.0% Duplication