title: How to use CodingKeys for enums conforming to Codable Protocol?
body: <p>I have an <code>EmailVerificationStatus</code> enum with an associated type of <code>String</code> that conforms to the <code>Codable</code> protocol:</p>
  
  <pre><code>enum EmailVerificationStatus: String, Codable {
      case unverified
      case verified
  }
  </code></pre>
  
  <p>The webservice I am working with sends those cases in uppercase (<code>UNVERIFIED</code> / <code>VERIFIED</code>). How can I use the <code>CodingKeys</code> enumeration to map that difference? Something like the following does not work:</p>
  
  <pre><code>enum CodingKeys: String, CodingKey {
      case unverified = "UNVERIFIED"
      case verified = "VERIFIED"
  }
  </code></pre>