[crd-generator] Implement SchemaSwap

[andreaTP]

Description

This is a Draft implementation of SchemaSwap.
The annotation serves to enable the use-case where you want to generate a valid CRD from a model that you don't own.

e.g.:
The model comes as a dependency on the classpath and you cannot add SchemaFrom annotations to it.

Issue found in (cc. @vmuzikar):
keycloak/keycloak#9759

I'm opening this PR as Draft to start the conversation regarding pros/cons and alternatives to this approach.
PRO:

• it enables to inject the equivalent of SchemaFrom annotations in a hierarchy without punctual changes
• the type checker is mostly preventing big issues
• [not implemented yet] we can implement a guard to throw an exception in case of fields/classes not found

CONS:

• the CRD api module cannot be easily executed anymore outside an AnnotationProcessor (the REFLECTION_CONTEXT doesn't preserve Annotations at the class level cc. @iocanel )
• Adding the APT Context subtly breaks the extraction of the Map value type

I'm happy to gather feedback and alternative proposals! cc. @metacosm @iocanel

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]

@iocanel would you be able to release a new version of sundrio containing the fix? 🙏 Thanks in advance!

[andreaTP]

Ready for review 🎉 cc. @metacosm
I'll add the documentation for this new annotation as soon as we agree this is the way to proceed.

[metacosm]

LGTM. Thank you!

[andreaTP]

Thanks @metacosm 🎉 , added the corresponding documentation.
It should be ready for final review/merge @manusa

[sonarcloud]

SonarCloud Quality Gate failed.   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
1 Code Smell

74.7% Coverage
0.0% Duplication

[andreaTP]

To backport this change to 5.12 we would need support from @iocanel 🙏
We need this PR backported to the 0.50 series of sundrio.