feat: support setting metadata.annotations

[porridge]

Needed for https://redhat.atlassian.net/browse/ROX-36583 which sets platform.stackrox.io/managed-services: true.

I only added annotations for now, as overriding all of metadata could lead to "creative" but fragile uses.

Tested in another PR.

Summary by CodeRabbit

• New Features
  • Central and SecuredCluster configurations now support optional metadata annotations.
  • Custom resources created from these configurations include the specified annotations, enabling additional metadata to be attached to deployed resources.
  • Annotation values are merged with existing resource metadata while preserving current configuration behavior.

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• internal/deployer/config.go

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📝 Walkthrough

Walkthrough

The change adds optional metadata annotations to Central and SecuredCluster configuration. Their custom-resource builders merge these annotations into resource metadata and report annotation merge errors.

Changes

Metadata annotations

Layer / File(s)	Summary
Configuration and custom-resource metadata internal/deployer/config.go	CentralConfig and SecuredClusterConfig now accept optional MetadataAnnotations. Their custom-resource builders merge the annotations into resource metadata and update merge error messages.

Estimated code review effort: 2 (Simple) | ~10 minutes

Merge Risk: ⚪ Minimal · up to 0d1c2

This change adds optional metadata annotations to Central and SecuredCluster custom resources without introducing a general metadata override. No current merge-readiness risk remains.

Suggested reviewers: mclasmeier

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 1…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: support for setting metadata annotations.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
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• Create PR with unit tests
• Commit unit tests in branch porridge/annotations

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[mclasmeier]

wondering about potential related use-cases in the future -- should we maybe
make this a nested central.metadata.annotations?

[porridge]

It crossed my mind, but I'm wondering if existence of central.metadata might make people incorrectly think anything in there is settable? 🤔

[mclasmeier]

Not saying that we have to do it this way, but I believe that this is something that should be coverable by docs and if people make wrong assumptions based on that... well. 🤷