getDesignations method
Will get a collection of PcoGivingDesignation objects (expecting many)
using a path like this: https://api.planningcenteronline.com/giving/v2/donations/1/designations
Implementation
Future<PcoCollection<PcoGivingDesignation>> getDesignations(
{PcoGivingDesignationQuery? query}) async {
query ??= PcoGivingDesignationQuery();
var url = '$apiEndpoint/designations';
return PcoCollection.fromApiCall<PcoGivingDesignation>(url,
query: query, apiVersion: apiVersion);
}