feat: Introduce Playwright for UI testing

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.

.gitignore

@@ -57,3 +57,8 @@ TestClass.class
 /.gitconfig
 
 webgoat.gitconfig
+node_modules/
+/test-results/
+/playwright-report/
+/blob-report/
+/playwright/.cache/