MAGETWO-82563: Coupon codes not showing in invoice [2.3-develop Backport] #11642

 - Merge Pull Request #11642 from crissanclick/magento2:InvoiceCouponCodesBackport
 - Merged commits:
   1. c8ebf87

Author: Oleksii Korshenko

app/code/Magento/Sales/etc/fieldset.xml

@@ -486,6 +486,12 @@
                 <aspect name="to_quote_address_shipping" />
                 <aspect name="to_cm"/>
             </field>
+            <field name="discount_description">
+                <aspect name="to_quote" />
+                <aspect name="to_invoice" />
+                <aspect name="to_shipment" />
+                <aspect name="to_cm" />
+            </field>
             <field name="shipping_amount">
                 <aspect name="to_quote_address_shipping" />
                 <aspect name="to_cm"/>