Tests Sources and Tests are Separated and on two Places

Demo Project

Demo project has its own repository, but there is a copy in /model-tests. This should be consolidated into one place.

E2E Tests

e2e tests are in two separate folders. /frontend-html/tests_e2e/ and /test/tests_e2e/. /frontend-html/tests_e2e/ contains the double amount of the tests, but /test/tests_e2e/ is used in PR checks. Also the tests are using different code. The tests should be consolidated into one place to avoid the confusion.