title: delete persisted object in one to one relation
body: <p>I'm using openjpa as a mapping layer and I have two models :
  user :</p>
  
  <pre><code>@Entity
  @Table(name = "USERS")
  public class User
  {
      @Id
      @GeneratedValue(strategy = GenerationType.SEQUENCE,generator = "user_id_gen")
      @SequenceGenerator(name = "user_id_gen", sequenceName = "manage.users_id", allocationSize=1)
      @Column(name = "id", nullable = false)
      private int _id;
  
      @OneToOne (cascade=CascadeType.ALL, fetch = FetchType.EAGER)
      @JoinColumn(name="fk_image_id", insertable=true, updatable=true, nullable = true)
      private Image _image;
  </code></pre>
  
  <p>and Image</p>
  
  <pre><code>@Entity
  @Table(name = "IMAGES")
  public class Image
  {
      @Id
      @GeneratedValue(strategy = GenerationType.SEQUENCE,generator = "images_id_gen")
      @SequenceGenerator(name = "images_id_gen", sequenceName = "manage.image_id", allocationSize=1)
      @Column(name = "id")
      private int _id;
  </code></pre>
  
  <p>it's unidirectional one to one relation.</p>
  
  <p>the problem is that I want to remove image without removing user and when I remove a user then remove image associated to him.</p>
  
  <p>right now when I delete an image it delete the user as well !!</p>