title: What is NSFaceIDUsageDescription - Face ID Usage Description Info.plist key?
body: <p>There is a new privacy <code>NSFaceIDUsageDescription</code> Info.plist key in the Xcode 9 GM where a developer supplies the usage description for the permissions alert. Does anyone have a link to docs on it? The plist view in Xcode summarizes it as: </p>
  
  <blockquote>
    <p>Privacy - Face ID Usage Description</p>
  </blockquote>