title: GraphQL Union and Input Type?
body: <p>Is it possible in GraphQL to have an input type that is also a union? </p>
  
  <p>Something like:</p>
  
  <pre class="lang-js prettyprint-override"><code>const DynamicInputValueType = new GraphQLUnionType({
    name: 'DynamicInputType',
    types: [GraphQLString, GraphQLFloat, GraphQLInt]
  })
  </code></pre>
  
  <p>but also able to be used as a input for a mutation?</p>