Consider consolidating Helm chart distribution to OCI-only (drop GitHub Pages)

[WentingWu666666]

Summary

Simplify the Helm chart release pipeline by consolidating distribution to OCI-only and dropping the GitHub Pages-based Helm repository.

Current State

The release workflow (release_images.yml) publishes the Helm chart to two distribution channels:

1. OCI registry (GHCR) via helm push ... oci://ghcr.io/documentdb/...
2. GitHub Pages via the repair_helm_pages_release.yml reusable workflow (publishes to the gh-pages branch with index.yaml)

Problem

Maintaining two distribution channels adds complexity:

• repair_helm_pages_release.yml is a 300+ line workflow dedicated to rebuilding/merging index.yaml and publishing to gh-pages
• The gh-pages branch must be maintained alongside the OCI registry
• Any issues with index.yaml require manual repair workflows
• OCI is the modern standard for Helm chart distribution (supported since Helm 3.8, which is 3+ years old)

Proposal

• Drop the GitHub Pages-based Helm repository and consolidate to OCI-only distribution
• Remove repair_helm_pages_release.yml and the publish-helm-pages job from release_images.yml
• Update documentation (README, install guides) to use OCI-based install commands exclusively:
  helm install documentdb oci://ghcr.io/documentdb/documentdb-operator --version <version>

Tradeoff

• Users lose helm repo add + helm search repo discoverability (must know the OCI URL)
• Requires Helm 3.8+ (released March 2022, widely adopted)
• Significantly simplifies the release pipeline

Note

The OCI URL and install command should be prominently documented in the README to compensate for the loss of helm search discoverability.

[alaye-ms]

We want to move to OCI only and will need to update the documentation to remove github pages references, as well as remove that from our workflows.