title: Auto add a coupon discount only when cart items are from 3 different product categories
body: <p>IN WooCommerce I would like to add 10% of discount with WooCommerce <strong>Coupon feature</strong>, only when customer purchases products from 3 different product categories <em>(like Category1, Category2, Category3)</em>.</p>
  
  <p>How this can be done with WooCommerce Coupon feature? </p>
  
  <p>Any help on this will be appreciated.</p>
  
  <p><strong>Update note:</strong> I only 3 parent product categories with no sub categories. Each product is assigned to one category. Some products are variable and some others are simple.</p>