title: Symfony FK Constraint Issue
body: <p>So I have a table schema that has users who can be friends.</p>
  
  <pre><code>User:
    actAs: { Timestampable: ~ }
    columns:
      name: { type: string(255), notnull: true }
      email: { type: string(255), notnull: true, unique: true }
      nickname: { type: string(255), unique: true }
      password: { type: string(300), notnull: true }
      image: { type: string(255) }
  
  FriendsWith:
    actAs: { Timestampable: ~ }
    columns:
      friend1_id: { type: integer, primary: true }
      friend2_id: { type: integer, primary: true }
    relations:
      User: { onDelete: CASCADE, local: friend1_id, foreign: id }
      User: { onDelete: CASCADE, local: friend2_id, foreign: id }
  </code></pre>
  
  <p>It builds the database correctly, but when I try to insert test data like:</p>
  
  <pre><code>User:
    user1:
      name: Danny Gurt
      email: comy19@gmail.com
      nickname: danny
      password: test1
    user2:
      name: Adrian Soian
      email: adriansoian@gmail.com
      nickname: adrian
      password: test1
  
  FriendsWith:
    friendship1:
      friend1_id: user1
      friend2_id: user2
  </code></pre>
  
  <p>I get this integrity constraint problem:</p>
  
  <pre><code>  SQLSTATE[23000]: Integrity constraint violation: 1452 Cannot add or update a child row: a foreign key constraint fails (`krowdd`.`friends_with`, CONSTRAINT `friends_with_ibfk_1` FOREIGN KEY (`friend1_id`) REFERENCES `user` (`id`) ON DELETE CASCADE)  
  </code></pre>
  
  <p>Any ideas?</p>
  
  <p>ADDITION:</p>
  
  <p>I noticed the generated sql code is only showing one constraint for the friends_with table:</p>
  
  <pre><code>ALTER TABLE friends_with ADD CONSTRAINT friends_with_friend2_id_user_id FOREIGN KEY (friend2_id) REFERENCES user(id) ON DELETE CASCADE;
  </code></pre>
  
  <p>Maybe this will help!</p>
  
  <p>Thanks!</p>