title: Assign many items to one category - OneToMany Relation
body: <p>I want to assign many items to one category. I'm using Symfony 2.6.7.</p>
  
  <p>I'm not at the owning side here. If I open this URI:</p>
  
  <p>/category/2/assign</p>
  
  <pre><code>[x] Item 1
  [x] Item 2
  (Save Button)
  </code></pre>
  
  <p>I have the possibility to chose many items with checkboxes.</p>
  
  <p>This is my db table "Item", where I want to connect the both:</p>
  
  <pre><code>id | category_id
  </code></pre>
  
  <p>It is an OneToMany relation, where One = Category and Many = Items.</p>
  
  <p>How can I assign the both here?</p>
  
  <p>It is already working, when I edit one item and than select a category to this item. Now I'm on the category side and here I want select many items to this one category. Can someone help, please? :-)</p>