title: graphql, union scalar type?
body: <p>The <code>payload</code> field can be <code>Int</code> or <code>String</code> scalar type.
  when I write it like union type:</p>
  <pre class="lang-js prettyprint-override"><code>const schema = `
    input QuickReply {
      content_type: String
      title: String
      payload: Int | String
      image_url: String
    }
  `
  </code></pre>
  <p>I got an error:</p>
  <pre class="lang-sh prettyprint-override"><code>GraphQLError: Syntax Error GraphQL request (45:18) Expected Name, found |
  
      44:     title: String
      45:     payload: Int | String
                           ^
      46:     image_url: String
  </code></pre>
  <p>It seems <code>GraphQL</code> does not support the union scalar type.</p>
  <p>So, how can I solve this situation?</p>