Write tests

Until now there are no tests regarding the backend. Therefore, this issue focuses on writing tests in the backend

For that add a new folder "Tests"

The following tests are important:

• check if docker container can be created
• connection to MongoDB
• check if authentication is working (skip for now)
• pull schema from git
• pull schema from git and save into db
• pull existing resources from git
• -> save the existing resources in DB
• create new entry in every category (schema conform, no authentication)
• create new entry in every category (schema conform, with authentication)
• create new entry in every category (invalid, with authentication)
• create new entry, then update this entry in every category (schema conform, authentication)
• create new entry, then update this entry in every category (invalid, authentication)
• create new entry, then update this entry in every category (invalid, no authentication)

Things that need to be done besides writing tests

• Create an environment where tests can run - local and on gitlab pipeline -> best is would be docker
• add the test suite into the gitlab pipeline -> should run on every commit

It is important not to reuse entries that you have created in an earlier test - tests should be written in a way that they can run without having dependencies on other tests