title: Graphql @include with expression
body: <p>I am implementing a query which should serve some fields in the response depending on user login status.</p>
  
  <p>To be specific, I want to get <strong>"pointRate"</strong> field only if <code>$authenticationToken</code> is passed &amp; would want to avoid passing <code>$authenticated</code> in below query. The reason I want to avoid sending <code>$authenticated</code> is client can do mistake by sending <code>$authenticated = true</code> but <code>$authenticationToken = null</code>.</p>
  
  <pre><code>query ToDoQuery($authenticationToken: String, $authenticated: Boolean!) {
      pointRate(accessToken: $authenticationToken) @include(if: $authenticated) {
          status
      }
  }
  </code></pre>