title: How to resolve subselections / relations in prisma (nested lists)
body: <p>Let's take an example from the github repo of prisma:</p>
  
  <p>We have a user, the user could have multiple posts, and one post could have multiple links.</p>
  
  <p>My goal is, to retrieve all posts and all links.
  This means, my response is a list (links) in a list (posts).</p>
  
  <p>I want to map the values I get back as two nested lists.</p>
  
  <p><strong>datamodel.prisma</strong></p>
  
  <pre class="lang-js prettyprint-override"><code>type User {
    id: ID! @id
    email: String! @unique
    name: String
    posts: [Post]!
  }
  
  type Post {
    id: ID! @id
    createdAt: DateTime! @createdAt
    updatedAt: DateTime! @updatedAt
    published: Boolean! @default(value: false)
    title: String!
    content: String
    author: User!
    links: [Link]!
  }
  
  type Link {
    id: ID! @id
    url: String
    title: String
    post: Post!
  }
  </code></pre>
  
  <p><strong>schema.graphql</strong></p>
  
  <pre class="lang-js prettyprint-override"><code>type Query {
    ...
  }
  
  type Mutation {
    ...
  }
  
  type Link {
    id: ID!
    url: String
    title: String
    post: Post!
  }
  
  type Post {
    id: ID!
    createdAt: DateTime!
    updatedAt: DateTime!
    published: Boolean!
    title: String!
    content: String
    author: User!
  }
  
  type User {
    id: ID!
    email: String!
    name: String
    posts: [Post]!
  }
  </code></pre>
  
  <p>I want to query <strong>all posts</strong> of a user, and all of the links for every post in the response.</p>
  
  <p>How would I query this request?</p>
  
  <pre><code>user {
    id
    posts {
      id
      links {
        id
      }
    }
  }
  </code></pre>
  
  <p>The above code snipper would not work.</p>
  
  <p><strong>EDIT</strong>
  I want to use the following:</p>
  
  <pre class="lang-js prettyprint-override"><code>User: {
    listPosts: (parent, args, context, info) {
      return context.prisma.posts().links()
    }
  }
  </code></pre>
  
  <p>So in my response (data in front-end via react-apollo Query Component), I want to map over posts AND the links in each post.</p>
  
  <p>BUT the links attribute in posts is null.</p>
  
  <p>Is there another way to achieve this?!</p>