HPZone_convert_dates: Converts all relevant columns in the dataset to Date types.
Description
Based on the available fields, a date for statistics is automatically generated, using the following logic:
If cases: Date_of_onset > Datum_melding_aan_de_ggd > Case_creation_date.
If situations: Start_date > Situation_creation_date
If enquiries: Received_on > Date_closed