[FEATURE] Try to add support for filtered Data Extensions / CSCLSROZ-438

[JoernBerkefeld]

Try to add support for filtered Data Extensions

[JoernBerkefeld]

groundwork down in #9 / PR #182
but so far no public API seen that could help here. instead, the GUI is using this endpoint to get the dataExtension details:
/internal/v1/customobjects/7191f458-4347-ee11-b863-48df37d1df5b