title: How to add more field in joined table "belongsToMany" in Sequelize?
body: <p>I have two table in sequelize</p>
  
  <ol>
  <li>Warehouse</li>
  <li>ProductItem</li>
  </ol>
  
  <p>Then I want to create a joined table name Inventory(productionItemId, warehouseId, qty)
  and Here is my current code:</p>
  
  <pre><code>Warehouse.belongsToMany(ProductItem, {
        as: "productItems",
        through: "inventories",
      });
  
  ProductItem.belongsToMany(models.Warehouse, {
        as: "warehouses",
        through: "inventories",
      });
  </code></pre>
  
  <p>The above code only create a joined table inventories(productionItemId,warehouseId). I would like to know how we can add extra field in inventories such as qty and so on.
  Appreciated for your help.
  Thank you</p>