Not possible to delete observations from DSD with mandatory group/series attributes
After observations + mandatory group/series attributes are loaded into dataflow it is impossible to delete these observations anymore with any of the supported format (xml,csv,edd) by repeating the same observations, but with EMPTY obs value + attribute values.
Most likely the bug is related to database schema change, where fact table was separated into seriesKey table + fact table.
Validation that prevents deletion (MandatoryAttributeWithNullValueAndExistingObservationData):
dotstatsuite-core-data-access\DotStat.Db\Validation\SqlServer\SqlKeyableDatabaseValidator.cs => CheckMandatoryAttributeKeysForDeletion
Expected result: it should be possible to delete observations uploading csv/xml/edd with empty obs value + attribute values.