title: NotificationCenter with EKEventStoreChanged notification called multiple times with different notifications
body: <p>First of all please note that I am not registered multiple times as observer as described in various other questions.</p>
  
  <p>When I change something in the native calendar application and return back to my app the selector gets called 4-5 times with different notifications.</p>
  
  <p>In <code>viewDidLoad</code> I remove any possible observers and register agian once:</p>
  
  <pre><code>NotificationCenter.default.removeObserver(self)
  NotificationCenter.default.addObserver(self, selector: #selector(reloadModelData(notification:)), name: Notification.Name.EKEventStoreChanged, object: nil)
  </code></pre>
  
  <p>The corresponding method:</p>
  
  <pre><code>@objc private func reloadModelData(notification: NSNotification) {
      debugPrint("method called \(notification)")
  }
  </code></pre>
  
  <p>Leads to this output</p>
  
  <blockquote>
    <p>"method called NSConcreteNotification 0x170246300 {name = EKEventStoreChangedNotification; object = ; userInfo = {\n    EKEventStoreChangedObjectIDsUserInfoKey =     (\n        \"x-apple-eventkit:///Location/p259707\",\n        \"x-apple-eventkit:///Event/p264955\"\n    );\n}}"
    "method called NSConcreteNotification 0x174258840 {name = EKEventStoreChangedNotification; object = ; userInfo = {\n    EKEventStoreChangedObjectIDsUserInfoKey =     (\n        \"x-apple-eventkit:///Location/p259707\",\n        \"x-apple-eventkit:///Event/p264955\"\n    );\n}}"
    "method called NSConcreteNotification 0x17024b250 {name = EKEventStoreChangedNotification; object = ; userInfo = {\n    EKEventStoreChangedObjectIDsUserInfoKey =     (\n        \"x-apple-eventkit:///Location/p259707\",\n        \"x-apple-eventkit:///Event/p264955\"\n    );\n}}"
    "method called NSConcreteNotification 0x174253b00 {name = EKEventStoreChangedNotification; object = ; userInfo = {\n    EKEventStoreChangedObjectIDsUserInfoKey =     (\n        \"x-apple-eventkit:///Location/p259707\",\n        \"x-apple-eventkit:///Event/p264955\"\n    );\n}}"</p>
  </blockquote>
  
  <p>Does anyone know how fix this. Meaning only receiving one single call of this observer when re-entering the app?</p>