title: With Ember Data, finding an actual record (not just a promise)
body: <p>I'm creating a record with a polymorphic belongsTo relationship. Its creation looks something like this:</p>
  
  <pre><code>this.get('store').createRecord('membership', { member: @get('session.currentUser') })
  </code></pre>
  
  <p>This throws the error:</p>
  
  <pre><code>You can only add a 'amorphous' record to this relationship
  </code></pre>
  
  <p>The User model does inherit from Amorphous, however. So I'm assuming the problem here is that I'm passing in a promise, rather than an actual model. Is there a way to get the resolved model before passing it in? Something like:</p>
  
  <pre><code>this.get('store').createRecord('membership', { member: @get('session.currentUser').
    then( function(user) {
      return user;
    })
  })
  </code></pre>
  
  <p>Unfortunately, this approach doesn't work. (It still passes the promise, not the resolved model.) But surely there's some way to force Ember Model to give you the resolved model?</p>