title: Save pushed id in Firebase Model
body: <p>I've got 2 firebase questions here : </p>
  
  <p>A/ Is it a good practice to programmatically <strong>copy the ID to the local model</strong> (excluded from the database), when parsing a value ?</p>
  
  <ul>
  <li>Frank, from Firebase, suggests that solution: <a href="https://stackoverflow.com/questions/43705871/save-userid-on-model-firebase/43707994#43707994">Save userId on model Firebase</a>  </li>
  </ul>
  
  <p>B/ Another solution would be to :  </p>
  
  <ul>
  <li>Generate a new key  </li>
  <li>Use that key and <strong>duplicate it to the model</strong>  </li>
  <li>Save the model (and the key) to database</li>
  </ul>
  
  <pre>
  val newPostRef = ref.child("posts").push()
  val key = newPostRef.key
  newPostRef.setValue(Post(key, "title", "content"))
  </pre>
  
  <p>Like this, the post id will be hold by the database model and parsed automatically with <strong>getValue(Post::class)</strong>.</p>
  
  <p>I can feel that is not a good solution, but please tell me why :)</p>
  
  <p>Regards</p>