Simplify helper with extracted method

app/helpers/admin/orders_helper.rb

@@ -7,17 +7,23 @@ module Admin
     # We exclude shipping method adjustments because they are displayed in a
     # separate table together with the order line items.
     def order_adjustments_for_display(order)
-      adjustments_for_display = order.adjustments + order.all_adjustments.payment_fee.eligible
+      order.adjustments +
+        voucher_included_tax_representations(order) +
+        order.all_adjustments.payment_fee.eligible
+    end
 
-      if VoucherAdjustmentsService.new(order).voucher_included_tax.negative?
-        adjustment = order.voucher_adjustments.first
-        adjustments_for_display << Spree::Adjustment.new(
-          label: I18n.t("admin.orders.edit.voucher_tax_included_in_price", label: adjustment.label),
+    def voucher_included_tax_representations(order)
+      return [] unless VoucherAdjustmentsService.new(order).voucher_included_tax.negative?
+
+      adjustment = order.voucher_adjustments.first
+
+      [
+        Spree::Adjustment.new(
+          label: I18n.t("admin.orders.edit.voucher_tax_included_in_price",
+                        label: adjustment.label),
           amount: adjustment.included_tax
         )
-      end
-
-      adjustments_for_display
+      ]
     end
   end
 end