refresh method
Manually trigger a refresh. Fetches the current FCM token and re-uploads
if it has changed since the last successful upload, or if the last upload
is older than _refreshInterval.
Implementation
Future<void> refresh(RelevaClient client) async {
_client = client;
try {
final token = await FirebaseMessaging.instance.getToken();
if (token == null || token.isEmpty) return;
await _maybeReregister(token);
} catch (e) {
debugPrint('Releva: PushTokenRefresher.refresh failed: $e');
}
}