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