title: Three way relationship
body: <p>Creating the following relationships</p>
  
  <p><code>bookmark.belongsToMany(tag, {through: 'BookmarkTag'});
   user.belongsToMany(bookmark, {through: 'UserBookmark'});
  </code></p>
  
  <p>Will create two relationshiptables</p>
  
  <p><code>BookmarkTag
  |bookmarkId|tagId</code></p>
  
  <p><code>UserBookmark
  |bookmarkId|userId</code></p>
  
  <p>i would like BookmarkTag to contain user id aswell so that i know which user added a tag to which bookmark</p>
  
  <p>BookmarkTag</p>
  
  <p>|bookmarkId|tagId|userId</p>
  
  <p>is that possible through sequelize associations</p>
  
  <p>fullcode</p>
  
  <pre><code>var bookmark = sequelize.define('Bookmark', {
    name: Sequelize.STRING,
    url: Sequelize.STRING
  });
  var tag = sequelize.define('Tag', {
    value: Sequelize.STRING
  });
  var user = sequelize.define('User', {
    email: Sequelize.STRING
  });
  bookmark.belongsToMany(tag, {through: 'BookmarkTag'});
  user.belongsToMany(bookmark, {through: 'UserBookmark'});
  sequelize.sync();
  </code></pre>