8.10 breaking-change communication: Helm v4 only

[Ian-wang-liyang]

Description

Customer-facing documentation and breaking-change communication for the Camunda 8.10 / chart 15.x Helm-v4-only transition. Scope is everything outside the camunda/camunda-platform-helm repo. In-repo docs (chart README, CONTRIBUTING.md) are tracked in camunda/camunda-platform-helm#6138.

Key facts to reuse verbatim across all artifacts:

• Camunda 8.9 (chart 14.x) is the last minor that supports Helm v3.
• Camunda 8.10 (chart 15.x) is Helm v4 only.
• No release-state migration is needed when switching from the Helm v3 CLI to v4 against the same cluster. Helm is client-side only; cluster state is unaffected.

Scope

Documentation

• Helm 4 guide + compatibility table — explicit statement: "Camunda 8.9 (chart 14.x) is the last minor that supports Helm v3; 8.10 (chart 15.x) is Helm v4 only."
• Self-Managed installation docs — Helm-v4-only banner on the 8.10 install page before any install command; replace or version-scope any Helm v3 example with Helm v4 syntax across all install docs.
• Self-Managed upgrade docs — explicit 8.9 → 8.10 note: "Switch to the Helm v4 CLI before upgrading. No release-state migration required."
• Reference architecture pages that mention Helm — update CLI version assumptions.
• New page: "Moving from Helm v3 CLI to v4 — no migration needed" — explain that helm is client-side only; the same release state works under both CLIs against the same cluster. No helm 3to4 step is required for Camunda charts.

Breaking-change communication

• 8.10 release announcement / release notes — explicit "Breaking change: Helm v4 required" entry. Owner: Release Notes / Distro.
• Blog post explaining the rationale, customer impact, and migration story (CLI swap, no release-state migration). Owner: Product Manager.
• 8.10 upgrade guide (Self-Managed admin guide) top-of-page note. Cross-link to the "no migration needed" page above.
• Internal field / CSM early communication — Slack + email to CSMs, PS, Support ahead of 8.10 GA. Owner: Product Manager.
• Internal field / CSM enablement one-pager / FAQ (also serves as Support canned-answer source):
  • "Can I use Helm v3 with 8.10?" — No. 8.9 is the last minor with Helm v3 support.
  • "Do I need to migrate cluster state from v3 to v4?" — No. Helm is client-side only.
  • "What's the upgrade path from 8.8/8.9 on Helm v3?" — Install the Helm v4 CLI, run helm upgrade against the existing release, then upgrade Camunda.

Acceptance criteria

• Searching docs for "helm 3" / "helm v3" surfaces only intentional, version-scoped references (e.g., 8.8 install).
• All five comms artifacts (release note, blog, upgrade guide note, internal early comms, CSM one-pager) published before 8.10 GA.
• CSM / Support / PS sign-off recorded on this ticket.

Out of scope (separate tickets)

• In-repo docs (chart README, CONTRIBUTING.md) — include extra documentation to explicitly call out that 8.10 (chart 15) is helm v4 only camunda-platform-helm#6138
• Chart-side CLI guard (fail when Helm CLI is not v4) — include an error when attempting to install chart 15 (8.10) with helm v3 CLI camunda-platform-helm#6137
• camundaPlatform.toYamlPretty Helm v3 quirk cleanup — drop toYamlPretty helm v3 compatibility since chart 15 is helm v4 only camunda-platform-helm#6139
• Version matrix page — [ISSUE] add helm v4 to chart version matrix camunda-platform-helm#5155

Labels

• kind/docs, target:8.10, component:distribution, component:qa (for support sign-off)