helm/v2-alpha: Add optional flag to generate a separate CRD chart (subchart/sibling chart) following Helm best practices

[camilamacedo86]

Add an optional mode/flag to scaffold a separate chart for CRDs (as a subchart or sibling chart). This is intended for advanced use cases and to align with Helm best practices around CRD installation and chart ordering.

References:

• Helm best practices: separate charts for CRDs is a documented approach: https://helm.sh/docs/chart_best_practices/custom_resource_definitions/
• Kubebuilder Helm plugin rationale for placing CRDs in templates today: https://book.kubebuilder.io/plugins/available/helm-v2-alpha.html
• User-facing confusion / install failures in: Question: helm - CRDs for first installation #5386

Motivation

Today the Helm plugin places CRDs under templates/crd so Helm applies them like normal resources and upgrades them (Helm’s crds/ directory installs once and does not manage upgrades). This is intentional.

However, there are common operational needs where users want:

• CRDs installed ahead of everything else (and potentially by cluster admins)
• a clean separation between “cluster-scoped API installation” (CRDs) and “namespaced operator installation”
• the ability to install CRs after CRDs are registered (without relying on hooks)

Helm docs explicitly describe the “separate charts” approach for CRDs/resources ordering.

Proposed feature

Introduce an optional flag/mode for the Helm plugin, for example:

• kubebuilder edit --plugins=helm/v2-alpha --crd-chart

Expected output (one possible layout)

subchart dependency

• dist/chart/
  • charts/<project>-crds/ (CRDs only, installed separately or as dependency)
  • (document recommended install ordering)

[camilamacedo86]

I am not sure if that is a good idea.
I think the problem that we need to figure out is "How I am can package the samples/CRs with the Helm Charts"? #5390