Add additional test scenarios #39

Problem description
The current test definitions are very simple, and are generally only testing schema compliance

Expected action

• Review the API Testing Guidelines to understand the CAMARA approach to defining tests
• Review the test definition templates, and adopt those relevant to this API
• Add tests which properly test the happy path for different mobile subscription states (e.g. if a SIM has a particular service suspended, does the API correctly return the status for that service for that SIM?)

Additional context
None