- create a guest user and modify function that adds users to the DB for testing
- improve code coverage of file endpoint tests and remove some obsolete code from file package
- add more error info if role validation fails in all endpoints
- change response of GET files to only return the file data and nothing else
- fix some bugs in file endpoints that became visible by the tests
- rename common package to database
- move all code not related to database to new helper package
- add more test in database package to improve code coverage
- add a new (own) package for AMQP client
