Migration test

[fbacall]

Summary of changes

• Adds a GitHub action to test database migrations, which runs if any files are changed under db/migrate/.

Motivation and context

I merged a PR with a broken migration

Checklist

• I have read and followed the CONTRIBUTING guide.
• I confirm that I have the authority necessary to make this contribution on behalf of its copyright owner and agree to license it to the TeSS codebase under the BSD license.

[Copilot]

Pull request overview

Adds a dedicated GitHub Actions workflow to validate that new database migrations can run cleanly by starting from the previously committed schema/migrations, helping prevent broken migrations from being merged.

Changes:

• Add .github/workflows/migration-test.yml workflow that triggers on changes under db/migrate/**.
• In the workflow, load the “previous” db/schema.rb (and migrations) into the test DB, then restore current migrations and run rails db:migrate.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.