title: rails jbuilder adding a root node
body: <p>I have the following jbuilder view:</p>
  
  <pre><code>json.array!(@users) do |json, user_object|
      json.partial! "api/v1/users/show", user: user_object
  end
  </code></pre>
  
  <p>to show each user data I render a partial of show to avoid duplication. This is all good but I also want to add a root node to the results to indicate some pagination data:</p>
  
  <pre><code>{
      total_pages: 1,
      total_records: 1000,
      users: {
          [ ...users here... ]
      }
  }
  </code></pre>