title: How to properly check if user has enabled "Allow Full Access" to custom keyboard extension
body: <p>I've tried prowling stackoverflow, and I've found some answers where you:</p>
  
  <p>1) update <code>UIPasteboard</code>, which I don't want to be altering for obvious reasons (<a href="https://stackoverflow.com/questions/39543113/allow-full-access-check-in-keyboards-ios10/39554347#39554347">Allow Full Access check in keyboards iOS10</a>)</p>
  
  <p>2) check <code>NSUserdefaults</code>,  drawbacks are the keyboard must be opened, and allow full access be enabled, and if it is later disabled, there will be the false value (<a href="https://forums.developer.apple.com/thread/28690" rel="nofollow noreferrer">https://forums.developer.apple.com/thread/28690</a>)</p>
  
  <p>Looking for iOS 10, Swift 3 solution. Thank you!</p>