Add integration tests with database connection

[matthiasschaub]

Currently, tests are mocking every database connection or are skipped (pytest.mark.skip in test_geodatabase.py).
In order to cleanup database-access-related code (especially avoid having 2 different persistence libraries),
the geo-database tests have to be reactivated first.

Tasks:

• reactivate existing geo-database tests
• consider using the PostGIS module of test containers
• find an appropriate subset for populating the test database
• try running the Jenkins build outside docker in order to avoid problems with test containers

Blocks #746

[mmerdes]

@joker234
It would be great if we could try to run the Jenkins build outside Docker some time as this would enable using the test containers library.

[joker234]

@joker234 It would be great if we could try to run the Jenkins build outside Docker some time as this would enable using the test containers library.

see PR #817