Setup an integration test to cover Staff management.

Implement tests that covers creation of a new staff member in different flavors (e.g. only mandatory fields, all fields) and all possible exceptions.

For more details about staff and date formatting see the API documentation.

https://demo.openmf.org/api-docs/apiLive.htm#staff

https://demo.openmf.org/api-docs/apiLive.htm#dates_and_numbers