[FIX] sale_project: clearer error message

The error message raised when linking a wrong SOline and a task used
unclear/incomplete information.

This commit improves the displayed message, replacing:
* the SO id by the SO reference, since record ids are not really useful to
    end users.
* the product name by its display name, to include variants details.

closes odoo/odoo#68041

X-original-commit: 8db6e654a50d38001c42247b33392aad90cab821
Signed-off-by: Victor Feyens (vfe) <vfe@odoo.com>

addons/sale_project/models/project.py

@@ -84,8 +84,8 @@ class ProjectTask(models.Model):
                 if not task.sale_line_id.is_service or task.sale_line_id.is_expense:
                     raise ValidationError(_(
                         'You cannot link the order item %(order_id)s - %(product_id)s to this task because it is a re-invoiced expense.',
-                        order_id=task.sale_line_id.order_id.id,
-                        product_id=task.sale_line_id.product_id.name,
+                        order_id=task.sale_line_id.order_id.name,
+                        product_id=task.sale_line_id.product_id.display_name,
                     ))
 
     @api.ondelete(at_uninstall=False)