Implement Test Cases for FHIR Patient Endpoint API

Implement Test Cases for the FHIR Patient Endpoint, allowing to automatically test whether API calls yield expected results when supplying Patient Resources to Mainzelliste.

A test case includes:

• a FHIR Resource that is send to the endpoint
• checking the response (i.e. check the return HTTP Status Code, check the response content, ..)
• optional: follow-up check in the database or with a subsequent API request (i.e. GET a previosly POSTed Patient Resource)

Include success cases as well as error cases (e.g. expect a graceful error on sending an empty request-body)