[FIX] sale: discount_amount in sale report

The discount_amount didn't consider the quantity on Sales Order Line.

e.g:

100€ | 10% discount | 8 products

--> discount_amount was 10 € instead of 80€

Fixes #43242

closes odoo/odoo#43587

Signed-off-by: Nicolas Martinelli (nim) <nim@odoo.com>

addons/sale/report/sale_report.py

@@ -89,7 +89,7 @@ class SaleReport(models.Model):
             sum(p.weight * l.product_uom_qty / u.factor * u2.factor) as weight,
             sum(p.volume * l.product_uom_qty / u.factor * u2.factor) as volume,
             l.discount as discount,
-            sum((l.price_unit * l.discount / 100.0 / CASE COALESCE(s.currency_rate, 0) WHEN 0 THEN 1.0 ELSE s.currency_rate END)) as discount_amount,
+            sum((l.price_unit * l.product_uom_qty * l.discount / 100.0 / CASE COALESCE(s.currency_rate, 0) WHEN 0 THEN 1.0 ELSE s.currency_rate END)) as discount_amount,
             s.id as order_id
         """