title: Swift Codable with reserved word
body: <p>I have a situation where the JSON being returned from an API has a field named extension, which is a reserved word in Swift. My codable is blowing up when I try to use it. </p>
  
  <p>I've searched for the last two hours, but I can't seem to find any solution. </p>
  
  <p>Has anyone run into this before:</p>
  
  <pre><code>public struct PhoneNumber: Codable {
  
      var phoneNumber: String
      var extension: String
      var isPrimary: Bool
      var usageType: Int
  }
  </code></pre>
  
  <p>Keyword 'extension' cannot be used as an identifier here</p>