title: UNUserNotification doesn't fire out my local notification under iOS 12
body: <p>In code I try to do it like this:</p>
  <pre><code>import UserNotifications
  
  if #available(iOS 10.0, *) {
          let center = UNUserNotificationCenter.current()
          center.requestAuthorization(options: [.alert, .sound]) { _, _ in }
          let content = UNMutableNotificationContent()
          content.title = &quot;Hello Staff&quot;
          content.body = &quot;Customer just ordered a milk with croissant&quot;
          content.sound = UNNotificationSound.default()
          let date = Calendar.current.dateComponents([.year, .month, .day, .hour, .minute, .second], from: Date(timeIntervalSinceNow: 10))
          let trigger = UNCalendarNotificationTrigger(dateMatching: date, repeats: false)
          let request = UNNotificationRequest(identifier: &quot;abcde&quot;, content: content, trigger: trigger)
          center.add(request)
  }
  </code></pre>
  <p>All happens within <code>AppDelegate</code>. But I can't see any local notification. Why?</p>