Deprecate postgres-13 job: removal scheduled for next release

[ZPascal]

Summary

Marks the `postgres-13` job as deprecated ahead of its removal in the next bosh release.

• `jobs/postgres-13/spec` — adds deprecation notice to the job description
• `jobs/postgres-13/templates/pre-start.erb` — emits a `WARNING` log line during `bosh deploy` so operators see it
• `docs/postgres-migration.md` — migration guide for upgrading from `postgres-13` to the `postgres` job (PostgreSQL 15), including automatic `pg_upgrade` on first deploy

Operators should switch to the `postgres` job. See `docs/postgres-migration.md` for the migration guide.

Related PRs

This is one of three independent PRs split from the original postgres-release migration:

• This PR: postgres-13 deprecation warning + migration guide (PR Deprecate postgres-13 job: removal scheduled for next release #2778)
• Companion: BRATS & CI/CD integration for postgres-release versions 15/16/17/18 (PR Add BRATS matrix tests for postgres-release versions 15/16/17/18 #2779)
• Companion: Remove postgres job, packages, and blob-bumping CI (PR Remove postgres job and packages; replace with postgres-release #2764)

Test plan

• `bosh deploy` with `postgres-13` job produces the deprecation WARNING in logs
• `docs/postgres-migration.md` is accessible

[coderabbitai]

Walkthrough

The postgres-13 job metadata and startup script now identify the job as deprecated and direct operators to cloudfoundry/postgres-release. A new migration guide documents manifest changes, automatic PostgreSQL 15 upgrades, and unchanged property namespaces.

Suggested reviewers: selzoc, benjaminguttmann-avtq

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title accurately summarizes the main change: deprecating postgres-13 and scheduling its removal in the next release.
Description check	✅ Passed	The description covers the change summary, related PRs, and test plan, but omits the release notes, breaking-change, tagging, and AI feedback sections.

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[Copilot]

Pull request overview

This PR deprecates the postgres-13 BOSH job ahead of its scheduled removal, by surfacing the deprecation both in the job metadata and during deployment/startup so operators see a clear migration signal.

Changes:

• Adds a deprecation warning message to the postgres-13 job pre-start script output.
• Adds a description field to jobs/postgres-13/spec marking the job as deprecated and directing operators to migrate.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
jobs/postgres-13/templates/pre-start.erb	Emits deprecation warning lines when the job runs its pre-start hook.
jobs/postgres-13/spec	Marks the job as deprecated via the job spec description string.

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[ZPascal]

Code review

Found 1 issue:

1. The "Switching from jobs/postgres-13" section tells operators to set `databases.version: 13`, but the guide itself states that postgres-release ships versions 15, 16, 17, and 18 — version 13 is not available. Any operator following this instruction will get a deployment failure. For a postgres-13 user, the migration requires a major-version upgrade (dump/restore or `pg_upgrade`), not a drop-in data directory swap.

bosh/docs/postgres-migration.md

Lines 62 to 66 in 7755c30

	## Switching from jobs/postgres-13
	Same as above, but set `databases.version: 13`.
	## In-place cutover procedure

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[coderabbitai]

Actionable comments posted: 3

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@docs/postgres-migration.md`:
- Around line 68-73: The migration procedure must explicitly handle legacy
postgres jobs: identify the existing PostgreSQL major version (typically 10 or
11), rename or migrate `/var/vcap/store/postgres` to the versioned directory
expected by postgres-release, and configure the matching source version so
`pg_upgrade` runs before selecting a newer target version. Update the steps
around `databases.version` and the deployment instructions to prevent fresh
initialization and preserve existing data.
- Around line 9-10: Update the supported-version statement in the PostgreSQL
migration documentation to accurately include PostgreSQL 13 if postgres-release
still ships it for pg_upgrade or in-place cutovers. Otherwise, remove or revise
the migration instructions that depend on version 13 so the documented supported
versions and procedures remain consistent.
- Around line 62-65: Update the “Switching from jobs/postgres-13” section to
avoid setting databases.version: 13 with cloudfoundry/postgres-release; document
a compatible release containing PostgreSQL 13 binaries, or replace the
pg_upgrade procedure with a pg_dump/pg_restore migration flow.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

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ℹ️ Review info

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Configuration used: Organization UI

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Run ID: d4960981-0b0f-4d4f-8f7b-dd45b21685d1

📥 Commits

Reviewing files that changed from the base of the PR and between 537c42e and 7755c30.

📒 Files selected for processing (3)

• docs/postgres-migration.md
• jobs/postgres-13/spec
• jobs/postgres-13/templates/pre-start.erb

[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@docs/postgres-migration.md`:
- Line 27: Update docs/postgres-migration.md so the file ends with exactly one
trailing newline, resolving the markdownlint MD047 violation without changing
its content.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Pro

Run ID: d4edf64a-144b-4a52-aca5-a19a52ca07e4

📥 Commits

Reviewing files that changed from the base of the PR and between 7755c30 and 4da127b.

📒 Files selected for processing (3)

• docs/postgres-migration.md
• jobs/postgres-13/spec
• jobs/postgres-13/templates/pre-start.erb