slapos_subscription_request: reduce the precision of the discount price

The idea is to reduce the risk of bad precision when building the related accounting transactions

master/bt5/slapos_subscription_request/SkinTemplateItem/portal_skins/slapos_subscription_request/SubscriptionRequest_createOpenSaleOrder.py

@@ -133,12 +133,17 @@ if (subscription_request.getPrice() != 0) and (0 < unused_day_count):
     stop_date=next_period_date,
     **open_order_edit_kw
   )
+  price = -subscription_request.getPrice() * (unused_day_count / (next_period_date - start_date))
+  precision = context.getQuantityPrecisionFromResource(subscription_request.getPriceCurrencyValue())
+  # Use currency precision to reduce the float length
+  price = float(('%%0.%sf' % precision) % price)
   discount_service = portal.restrictedTraverse('service_module/slapos_discount')
   sale_packing_list.newContent(
     portal_type="Sale Packing List Line",
     resource_value=discount_service,
-    quantity=unused_day_count / (next_period_date - start_date),
-    price=-subscription_request.getPrice(),
+    # Use a quantity of 1 to be able to count how many discount were distributed
+    quantity=1,
+    price=price,
     quantity_unit_value=discount_service.getQuantityUnitValue(),
     base_contribution_list=discount_service.getBaseContributionList(),
     use=discount_service.getUse(),