title: How to have GraphQL enum resolve Strings
body: <p>Previously, I just typed my <code>input KeyInput</code> as <code>mode: String!</code>, and I'm looking to change the type from String! to a custom enum.  </p>
  
  <p>I have the tried following schema:</p>
  
  <pre><code>enum Mode= {
      test
      live
  }
  
  input KeyInput = {
      mode: Mode!
  }
  
  type Key {
      name,
      mode
  }
  
  type Query {
      Keys(input: KeyInput): [Key]
  }
  </code></pre>
  
  <p>And my query looks like this:</p>
  
  <pre><code>query{
       Keys(input: {mode: "test"}){
          name
       }
  }
  </code></pre>
  
  <p>However, I get the following error:</p>
  
  <pre><code>      "message": "Expected type Mode!, found \"test\"; Did you mean the enum value test?"
  </code></pre>
  
  <p>Is it possible to have enum values resolve String values?  If I remove the quotes from the input, it will work.  However, I need to be able to continue to resolve the Mode as Strings.  </p>