title: ManyToMany self-referenced with extra column in Doctrine
body: <p>I have problem which is easy to solve with pure SQL but I need to solve it with Doctrine in YAML.</p>
  
  <p>I have well known db tables users and friends. Where users table has primary key <code>user_id</code> and friends has <code>friend_id</code> and <code>friend_with_id</code> which uses user_id from table user. My problem starts when I need to add there one more column mood. With SQL I add to table friends onemore column named mood and it's done with doctrine I can't find any solution.</p>
  
  <p>For better understanding I add db scheme:
  <img src="https://i.stack.imgur.com/lu4yw.png" alt="enter image description here"></p>