Incorporate test mock that 3rd parties can use

Description

To aid developers using this library refactor and make available the mock that this library's tests use. An initial version has been created here: https://gitlab.developers.cam.ac.uk/uis/devops/laboratory-allocator/lab-allocator/-/blob/727b95d775bf446c83c8d2a29a064b6971d99700/student/tests/test_get_student.py#L8.

Further details

Downstream services need a way to test their code that interacts with this library and also to verify their usage of this library's interface is correct. Service local mocks only verify that the interface of the library works as the person writing the mock understands it.

Making a shared mock available creates a common understanding of the interface that can be tested against.

Task list

• refactor current tests with refactored mock, moving per test data into each individual test (e.g. https://gitlab.developers.cam.ac.uk/uis/devops/laboratory-allocator/lab-allocator/-/blob/727b95d775bf446c83c8d2a29a064b6971d99700/student/tests/test_get_student.py#L106)
• make the mock available via the published library