[BACKEND] Change booking dates endpoints

[jeffplays2005]

This is not an urgent ticket

Would be a good edit to make the endpoints before handover: POST /bookings/make-dates-available/unavailable -> PATCH /admin/bookings/dates

BEFORE MERGING

• [ ] Integration test written for services
• [ ] Schemas annotated if adding new models
• [ ] Code generation run (hint: yarn workspace server tsoa spec-and-routes)
• [ ] Appropriate mocks created where possible
• [ ] PR Reviewed (For non-trivial changes)
• [ ] Changes tested after rebasing on master or merging in master (hint: git fetch origin master:master, then git rebase master or git merge master)
• [ ] All required PR checks passing