Allow the order updater to handle non-persisted line items

In an associated change we made the `CreateDiscountedItem` benefit
create in-memory line items. That causes an issue during the
recalculation of the item totals.

Co-authored-by: benjamin wil <benjamin@super.gd>
Co-authored-by: Kendra Riga <kendra@super.gd>
Co-authored-by: Noah Silvera <noah@super.gd>
Co-authored-by: Jared Norman <jared@super.gd>

Author: 5 people

core/app/models/spree/order_updater.rb

@@ -232,12 +232,11 @@ def recalculate_item_totals
 
         next unless item.changed?
 
-        item.update_columns(
+        item.assign_attributes(
           promo_total:          item.promo_total,
           included_tax_total:   item.included_tax_total,
           additional_tax_total: item.additional_tax_total,
-          adjustment_total:     item.adjustment_total,
-          updated_at:           Time.current,
+          adjustment_total:     item.adjustment_total
         )
       end
     end

legacy_promotions/app/patches/models/solidus_legacy_promotions/spree_order_updater_patch.rb

@@ -30,15 +30,14 @@ def recalculate_item_totals
           reject(&:included?).
           sum(&:amount)
 
-        if item.changed?
-          item.update_columns(
-            promo_total:          item.promo_total,
-            included_tax_total:   item.included_tax_total,
-            additional_tax_total: item.additional_tax_total,
-            adjustment_total:     item.adjustment_total,
-            updated_at:           Time.current,
-          )
-        end
+        next unless item.changed?
+
+        item.assign_attributes(
+          promo_total:          item.promo_total,
+          included_tax_total:   item.included_tax_total,
+          additional_tax_total: item.additional_tax_total,
+          adjustment_total:     item.adjustment_total
+        )
       end
     end
     Spree::OrderUpdater.prepend self