Example/Template for cross dbms testing (functional tests) missing

[sbuerk]

Goal

I as a developer want to have cross dbms testing

Acceptance Criteria

• [ ] testing cross dbms is implemented
• [ ] functional tests are running

Additional Information

To fullfill the mission of this project cross dbms testing (ex functional tests) should be showcased.

Currently in the github worflows it is only tested with one mysql version. This should be extended to test with other supported dbms also (at least sqlite, mariadb/mysql(both), postgres).