Instead of using Robot Framework which does not run during a `mvn install`. Playwright seems to be the better approach. We can now write them as normal JUnit test and they are executed during a build.
Additionally this PR solves some interesting bugs found during writing Playwright tests:
- A reset of a lesson removes all assignments as a result another user wouldn't see any assignments
- If someone solves an assignment the assignment automatically got solved for a new user since the assignment included the `solved` flag which immediately got copied to new lesson progress.
- Introduction of assignment progress linking a assignment not directly to all users.
