title: How to update an array in Sequelize Postgres
body: <p>I have a user model in Sequelize for a Postgres db: </p>
  
  <pre><code>var User = sequelize.define('User', {
  fb_id: DataTypes.STRING,
  access_token: DataTypes.TEXT,
  first_name: DataTypes.STRING,
  last_name: DataTypes.STRING,
  email: DataTypes.TEXT,
  profilePictureURL: DataTypes.TEXT,
  library: DataTypes.ARRAY(DataTypes.STRING)
  }, {
  underscored: true,
  classMethods: {
    associate: function(models) {
  
     }
   }
    });
  </code></pre>
  
  <p>I am trying to update the library field by adding ISBNs to the array. This is the code for my POST request: </p>
  
  <pre><code>req.user.library.push(req.body._isbn); // adding the posted ISBN to the user object in my express-session
  
  User.findOrCreate({where: {fb_id: req.user.fb_id}, 
          defaults: {
              access_token :      req.user.access_token,                 
              first_name :        req.user.first_name,
              last_name :         req.user.last_name,
              email :             req.user.email, 
              profilePictureURL : req.user.profilePictureURL,
              library: req.user.library // new library object
          }})
          .spread(function (updatedUser, created){
              res.status(200).json(updatedUser);
          }).error(function(err){
              res.status(500).json(err);
          });
  </code></pre>
  
  <p>There is no error, but the library field is not updated after checking the updatedUser object. How do I correctly update an array field in Sequelize?</p>