title: Doctrine2.3 and OneToOne cascade persist doesn't seem to work
body: <p>I have two entites (User and UserPreferences) that I want to map OneToOne unidirectional.</p>
  
  <p>The code looks something like this:</p>
  
  <pre><code>/**
   * @ORM\Table("users")
   * @ORM\Entity
   */
  class User
  {
      /**
       * @ORM\Column(name="id", type="integer")
       * @ORM\Id
       */
      protected $id;
  
      ...
  
      /**
       * @ORM\Column(name="user_preferences_id", type="integer")
       * @ORM\OneToOne
       * (
       *      targetEntity="UserPreferences",
       *      cascade={"persist"}
       * )
       */
      protected $userPreferences;
  
      public function __construct() {
          $this-&gt;userPreferences = new UserPreferences();
      }
  }
  
  
  /**
   * @ORM\Table("user_preferences")
   * @ORM\Entity
   */
  class UserPreferences extends UserPreferencesEntity
  {
      /**
       * @ORM\Id
       * @ORM\Column(name="user_id", type="integer")
       * @ORM\GeneratedValue(strategy="AUTO")
       */
      protected $id;
  
      ...
  }
  </code></pre>
  
  <p>Now when a new User is created, userPreferences is initialized with a new UserPreferences object. When trying to persist <code>user</code>, Doctrine throws an Exception, claiming </p>
  
  <p><code>A new entity was found through the relationship '...\Entity\User#userPreferences' that was not configured to cascade persist operations for entity: ...\Entity\UserPreferences@000000003ae25e5700000000a6eaafc9. To solve this issue: Either explicitly call EntityManager#persist() on this unknown entity or configure cascade persist  this association in the mapping for example @ManyToOne(..,cascade={"persist"}).</code></p>
  
  <p>But what else should I do? User#userPreferences is configured to cascade persist but it doesn't. Am I getting something wrong here? </p>