Implement "DMS Showcase" cypress test

[simonhir]

Is your feature request related to a problem? Please describe.

As described in the internal test documentation the test cases should be implemented in cypress for automated testing.
In this task the "DMS Showcase" test should be implemented.

Describe the solution you'd like

• The "DMS Showcase" test case should be implemented in digiwf-cypress
• The test case should use page object model, meaningful selectors and inheritance
• It can be executed stable lokal and on the digiwf-test env

Acceptance Criteria

• Test case "DMS Showcase" is implemented with cypress
• Test runs stable and matches internal requirements/best practices

Additional context

#1396

[markostreich]

Auch überlegen, wie wir mit Datenmüll im DMS umgehen.