title: How to dynamically update fields on duplicate key with Sequelize.bulkCreate
body: <p>How would one implement `ON DUPLICATE KEY UPDATE score = score + VALUES(score)</p>
  <p>My pseudocode:</p>
  <pre><code>  await User.bulkCreate(
      [{...}],
    {
      updateOnDuplicate: ['score']   // This only overwrites the previous value 
    }
    )
  </code></pre>