Turn ATKIS importer into another pseudo-harvester to automatically keep this up-to-date.
This is closely modelled on the newly introduced WikiData harvester.
If this is merged, we can drop the atkis_aktualisieren
CI job, c.f. https://gitlab.opencode.de/umwelt-info/infrastruktur/testbetrieb/-/blob/main/metadaten/ci.yml#L141-L152