Fix flaky tests by making school teacher ID lookup deterministic

[zetter-rpf]

Example failure - https://github.com/RaspberryPiFoundation/editor-api/actions/runs/22571941511/job/65381726124

This was making the order that teaches returned non-deterministic, which was causing intermittent test failures.

The test that was failing was the 'SchoolTeacher::List when successful when not passing teacher_ids returns a successful response with school teachers' test in ./spec/concepts/school_teacher/list_spec.rb.

[cursor]

Cursor Agent can help with this pull request. Just @cursor in comments and I'll start working on changes in this branch.
_{Learn more about Cursor Agents}

[github-actions]

Test coverage

89.92% line coverage reported by SimpleCov.
Run: https://github.com/RaspberryPiFoundation/editor-api/actions/runs/22586956044

[Copilot]

Pull request overview

This PR makes the teacher ID lookup used by SchoolTeacher::List deterministic to eliminate intermittent test failures caused by non-deterministic role ordering.

Changes:

• Order teacher Role records by id before plucking user_ids when teacher_ids aren’t provided.

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[mwtrew]

Is it safe to get rid of the [...]&.[...]? I'm not sure if a school can have no teachers, though.

[zetter-rpf]

Is it safe to get rid of the [...]&.[...]? I'm not sure if a school can have no teachers, though.

Yes, the query isn't executed until pluck is called on it. If there are no records matching, the result will be []. There's no point in adding the &. it will always be acting on a truthy value (the active record relation object that represents the query)