Using SQLite for testing base classes

[wahani]

In #16 we will get some duplication in the test infrastructure. I suggest to change the test setup for the base classes and use SQLite instead of a mariadb db in a container.

• The mariadb container adds a lot of overhead to the tests.
• We will speed up the tests considerably.
• We would address the argument in https://github.com/_render_node/MDIzOlB1bGxSZXF1ZXN0UmV2aWV3VGhyZWFkMjQ0MzkwNzUyOnYy/pull_request_review_threads/discussion_