subscribe method
Implementation
String subscribe(
void Function(OpenFeatureEvent) handler, {
EventFilter? filter,
bool autoAck = true,
}) {
final subscription = EventSubscription(
id: DateTime.now().millisecondsSinceEpoch.toString(),
filter: filter ?? const EventFilter(),
handler: handler,
autoAck: autoAck,
);
_subscriptions[subscription.id] = subscription;
return subscription.id;
}