docs: references to a private planning repository in docs, code comments, values.yaml and tests #922

Problem

The README, CHANGELOG, UPGRADE.md, docs, code comments, values.yaml files, chart examples and test scripts of this public repository reference a private planning repository (by issue number and decision label). The references are unreadable for everyone outside and name an internal repository.

Proposed solution

After the docs rewrite in #895 has merged, replace each such reference with the public issue that carries the decision, or with the decision's substance in one clause: first in README, CHANGELOG, UPGRADE.md and docs/, then in code comments, values.yaml, chart templates, examples and tests.

Acceptance criteria

• No file of the repository references a private planning repository.
• Every replaced reference keeps its meaning.

Written by an agent.