Redirect renamed project slugs to current page (#944)

[jonfroehlich]

Summary

Renaming a project changes its short_name (the URL slug), which previously made the old /project/<old-slug>/ URL hard-404 — breaking external links and search results. This came out of the #1142 SEO audit, where /project/mapoutloud/ and /project/mixed-ability-art/ were sitting in Google's "Not found (404)" bucket.

This adds a former-slug → current-page 301 redirect system so renames no longer break URLs, and backfills the known historical renames. Closes #944.

How it works

• ProjectAlias model (website/models/project_alias.py): maps a retired slug → its Project.
• Auto-capture (Project.save()): when short_name changes, the old slug is recorded as an alias pointing at the project; a reclaimed slug clears its old alias so it can't self-redirect.
• View redirect (website/views/project.py): on a slug miss, look up the alias and 301-redirect to the canonical singular /project/<slug>/. A live project always wins over an alias.
• Uniqueness (clean() on both models): the combined live-slug + alias namespace stays unique, so a slug always resolves to exactly one destination.
• Admin (ProjectAliasInline): editors see auto-captured aliases and can add historical ones by hand.
• Seed command (seed_project_aliases, wired into docker-entrypoint.sh): idempotently backfills renames done before auto-capture existed:
  • mapoutloud → geovisally
  • mixed-ability-art → artinsight
  • smarthomedhh → homesound

Testing

• New website/tests/test_project_aliases.py (13 tests): auto-capture on rename, 301 redirect, slug reclaim (no loop), namespace uniqueness, visibility, seed idempotency, and 404 on unknown slugs.
• Full suite green (531 passed, 8 skipped) via --settings=makeabilitylab.settings_test.
• Verified live on the dev server: a temporary alias 301-redirected to its project page.

Post-deploy verification

Once on master → test (then tag → prod), confirm:

• curl -sI .../project/mapoutloud/ → 301 → /project/geovisally/
• curl -sI .../project/mixed-ability-art/ → 301 → /project/artinsight/
• curl -sI .../project/smarthomedhh/ → 301 → /project/homesound/

Then re-run GSC "Validate Fix" on the Not found (404) group.

Notes

• No hand-written migration is committed (per-env website/migrations/ is gitignored; the entrypoint regenerates + the test suite builds from models).
• Future renames done in admin now record their own aliases automatically — no seed entry needed.

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