title: Symfony2 Entity validation — one has to be true
body: <p>I have a problem with the validation of Symfony. I have a form which is of the type <code>User</code> and the user maps some other stuff (like <code>Addresses</code>, <code>Phone</code>s etc.)</p>
  
  <p>Now I want to force the creator of the user that he makes one of the <code>Addresses</code>/<code>Phones</code> the primary one (the entity has a field for that).</p>
  
  <p>How can I solve this? So only one of the OneToMany Entitys (one of the <code>Addresses</code>) needs to be a primary one. And assure that it will be always at least one.</p>