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