retrieveAdministrativeUnitNameWithExistentCartographicBoundaries

Retrieves a Flow of Pair<AdministrativeUnitName, List<CartographicBoundary>>.

This method retrieves AdministrativeUnitName data along with any existing associated CartographicBoundary entities. It utilizes Flow to emit data asynchronously.

To avoid emitting duplicate AdministrativeUnitName entries, it maintains a set of IDs (administrativeUnitNameIDS). Only new (unseen) entries are emitted.