code: def ecommerce_coupon_url(self, instance):
          
          if not instance.entitlement_id:
              return "N/A"
  
          return format_html(
              '<a href="{base_url}/coupons/{id}" target="_blank">View coupon "{id}" details</a>',
              base_url=settings.ECOMMERCE_PUBLIC_URL_ROOT, id=instance.entitlement_id
          )
docs: Instance is EnterpriseCustomer. Return e-commerce coupon urls.