title: Rails: include related object in JSON output
body: <p>I have a note class that belongs to a user (ie a user can create many notes).</p>
  
  <p>clip from my notes controller</p>
  
  <pre><code>class NotesController &lt; ApplicationController
    before_filter :authenticate_user!
    respond_to :html, :xml, :json
  
    # GET /notes
    # GET /notes.xml
    def index
      @notes = Note.includes(:user).order("created_at DESC")
      respond_with @notes
    end
  </code></pre>
  
  <p>When I ask for the index in json results for example /notes.json, it returns the notes but only returns user_id for the user object.  I would like it to also include user.username (and would be curious how to have the whole user object embedded).</p>
  
  <p>Bonus question:  I could not find a way to make the column show as author_id and have it relate back to user.  If this is easy to do, how do you do it?</p>