title: Exception using nested Input Types in GraphQL and Spring Boot
body: <p>I'm trying to create a Mutation that receives an input type like this:</p>
  
  <pre><code>input Cart {
      items: [CartItem!]!
      client: String!
  }
  
  input CartItem {
      productId: Int!
      qty: Int!
  }
  </code></pre>
  
  <p>And my Mutation goes like this:</p>
  
  <pre><code>type Mutation {
      createOrder(cart: Cart!): Order!
  }
  </code></pre>
  
  <p>But when I try to run my Application I get the following exception:</p>
  
  <pre><code>Caused by: com.coxautodev.graphql.tools.SchemaError: Expected type 'CartItem' to be a GraphQLOutputType, but it wasn't!  Was a type only permitted for object types incorrectly used as an input type, or vice-versa?
  </code></pre>
  
  <p>What's going on?</p>