feat(back-office-subscribers): add exam timetable unpublish function

[emil-placheta]

Describe your changes

Ticket: https://pins-ds.atlassian.net/browse/ASB-2286

Infra PR:

Useful information to review or test

1. Follow the readme on the back-office subscribers function to set it up
2. Run azurite npx azurite and this function npx func start --functions nsip-exam-timetable-unpublish
3. Make a POST request to http://localhost:7071/admin/functions/nsip-exam-timetable-unpublish with this body:

{
    "input": "{\"caseReference\":\"mock-id\"}"
}

to test that the error is thrown when case reference is missing:

{
    "input": "{\"notCaseReference\":\"mock-id\"}"
}

Type of change 🧩

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Other (please explain in the description section above)

Checklist before requesting a review

• I have performed a self-review of my own code
• I have double checked this work does not include any hardcoded secrets or passwords
• I have made corresponding changes to the documentation
• I have provided details on how I have tested my code
• I have referenced the ticket number above
• I have provided a description of the ticket
• I have included unit tests to cover any testable code changes

[Yakitrak]

LGTM

[AnthonyJWalsh]

🎉 This PR is included in version 1.8.0 🎉

The release is available on GitHub release

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[AnthonyJWalsh]

🎉 This PR is included in version 2.18.0 🎉

The release is available on GitHub release

Your semantic-release bot 📦🚀

[AnthonyJWalsh]

🎉 This PR is included in version 2.23.0 🎉

The release is available on GitHub release

Your semantic-release bot 📦🚀