feat(helm): add values schema and chart-testing lint (#381 M2, M3)

[WentingWu666666]

Part of the GA-readiness chart audit (#381) — items M2 and M3.

What this PR does

Adds Helm values validation and chart-testing lint to the operator chart, aligning with upstream CloudNative-PG chart practice.

M2 — values.schema.json

Adds a draft-07 JSON Schema for values.yaml. Helm automatically validates user-supplied values against it on install / upgrade / template / lint, so mistakes fail fast with an actionable message instead of becoming runtime errors. Examples now rejected up front:

• --set replicaCount=one → got string, want integer
• --set image.documentdbk8soperator.pullPolicy=Sometimes → value must be one of 'Always', 'IfNotPresent', 'Never'
• --set replicaCont=2 (typo) → additional properties 'replicaCont' not allowed

The schema is strict at the root (typed keys, no unknown top-level properties) and lenient for Kubernetes-native nested structures (resources, security contexts, affinity) and the bundled cloudnative-pg subchart values.

M3 — chart-testing lint in CI

Adds a Helm Chart Lint (chart-testing) job to test-unit.yml using the standard helm/chart-testing action — the same tool CNPG uses in its lint.yml. ct lint runs helm lint, validates values against the schema (M2), and lints chart YAML/Chart.yaml.

• .github/configs/ct.yaml — chart-testing config (explicit chart path, CNPG dependency repo, maintainer/version checks disabled).
• .github/configs/lintconf.yaml — lenient yamllint config (structural checks only).
• operator/documentdb-helm-chart/ci/*-values.yaml — value combinations ct lint renders and schema-validates: baseline, walReplica=true, and a custom-namespace + imagePullSecrets + scheduling-overrides case.

Why split from #384

Kept separate from the plugin-probes PR (#384) so each change reviews independently; M2's generated schema is a large additive file that would otherwise bury the probe change.

Local verification

• ct lint --config .github/configs/ct.yaml passes for values.yaml and all three ci/*-values.yaml files.
• Schema rejects bad types, invalid enums, and unknown keys (verified via helm template --set).
• helm lint clean; helm unittest — 82 tests pass.

Notes

• The pre-existing values.yaml uses CRLF line endings; normalizing that is out of scope, so the new-lines yamllint rule is disabled rather than reformatting the file in this PR.
• This PR is based on main and is independent of feat(helm): add readiness probes for plugin sidecars #384.

Tracking

• Helm chart improvements for GA readiness #381 (GA chart audit, items M2 and M3)

[Copilot]

Pull request overview

Adds Helm chart values validation and CI linting for the DocumentDB operator Helm chart to catch misconfigurations early and align with upstream CloudNative-PG chart practices.

Changes:

• Introduces values.schema.json (draft-07) to validate values.yaml and user overrides at install/upgrade/template/lint time.
• Adds chart-testing (ct lint) as a GitHub Actions job to lint and schema-validate the chart under multiple value combinations.
• Adds chart-testing configuration + yamllint configuration and three ci/*-values.yaml render cases.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
operator/documentdb-helm-chart/values.schema.json	Adds a strict top-level JSON Schema for Helm values with lenient Kubernetes-native nested structures and passthrough CNPG subchart values.
operator/documentdb-helm-chart/ci/default-values.yaml	Baseline values file for ct lint rendering/schema validation.
operator/documentdb-helm-chart/ci/walreplica-values.yaml	Values variant to exercise the WAL replica render path in ct lint.
operator/documentdb-helm-chart/ci/custom-namespace-values.yaml	Values variant to exercise namespace override, imagePullSecrets, and scheduling overrides in ct lint.
.github/workflows/test-unit.yml	Adds a “Helm Chart Lint (chart-testing)” CI job running ct lint with repo configs.
.github/configs/ct.yaml	Configures chart-testing to lint the operator chart deterministically with CNPG repo wiring and yamllint settings.
.github/configs/lintconf.yaml	Provides a deliberately lenient yamllint config for chart-testing focused on structural correctness.

[documentdb-triage-tool]

🤖 Auto-triaged by documentdb-triage-tool.

Applied: CI/CD, enhancement
Project fields suggested: Component ci · Priority P2 · Effort L · Status In Progress
Confidence: 0.82 (mixed)

Reasoning

component from path globs (ci); effort from diff stats (306+0 LOC, 7 files); LLM: Adds Helm values JSON Schema validation (M2) and chart-testing lint CI job (M3) across multiple files — CI workflow, chart configs, and schema — as part of a GA-readiness audit milestone.

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