[REF] event_sale: correctly compute discount for event tickets

Discount wasn't computed the same way in backend sale flows and e-commerce flows.
Now the pricelist discount policy will be considered in the core logic of
event_sale.

Part-of: odoo/odoo#82374

addons/event_sale/models/event_ticket.py

@@ -53,8 +53,6 @@ class EventTemplateTicket(models.Model):
     def _compute_price_reduce(self):
         for ticket in self:
             product = ticket.product_id
-            # TODO drop price field usage
-            # and ideally remove this whole price_reduce logic
             # seems strange to not apply pricelist logic but still use pricelist discount...
             discount = (
                 product.lst_price - product._get_contextual_price()

addons/event_sale/models/sale_order.py

@@ -134,14 +134,9 @@ class SaleOrderLine(models.Model):
         super(SaleOrderLine, self-event_lines)._compute_price_unit()
         for line in event_lines:
             if not line.product_id or line._origin.product_id != line.product_id:
+                # Note: this also computes the price for new lines :)
                 super(SaleOrderLine, line)._compute_price_unit()
 
-    @api.depends('event_ticket_id')
-    def _compute_discount(self):
-        """Do not compute the discount on event lines, it's always included in the price."""
-        event_lines = self.filtered('event_ticket_id')
-        super(SaleOrderLine, self-event_lines)._compute_discount()
-
     @api.depends('event_ticket_id')
     def _compute_name(self):
         """Override to add the compute dependency.
@@ -173,12 +168,13 @@ class SaleOrderLine(models.Model):
 
     def _get_display_price(self):
         if self.event_ticket_id and self.event_id:
-            # FIXME this is strange
-            # price_reduce is the price after discount
-            # shouldn't we leave the discount computation to sale
-            # and use the non reduced price here (aka price field)
-            return self.event_ticket_id.with_context(
+            event_ticket = self.event_ticket_id.with_context(
                 pricelist=self.order_id.pricelist_id.id,
-                uom=self.product_uom.id).price_reduce
+                uom=self.product_uom.id
+            )
+            if self.order_id.pricelist_id.discount_policy == 'with_discount':
+                return event_ticket.price_reduce
+            else:
+                return event_ticket.price
         else:
             return super()._get_display_price()