[FIX] sale: fix usage of message_post_with_template in batch

Sending confirmation email is generally done on a singleton recordset but
some calls could end up calling in batch. Anyway better safe than sorry.

Task-2710804 (Mail: Clean MailThread API)

closes odoo/odoo#100137

Related: odoo/enterprise#31301
Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>

addons/sale/models/sale_order.py

@@ -832,9 +832,11 @@ class SaleOrder(models.Model):
             # sending mail in sudo was meant for it being sent from superuser
             self = self.with_user(SUPERUSER_ID)
 
-        mail_template = self._get_confirmation_template()
-        if mail_template:
-            self.with_context(force_send=True).message_post_with_template(
+        for sale_order in self:
+            mail_template = sale_order._get_confirmation_template()
+            if not mail_template:
+                continue
+            sale_order.with_context(force_send=True).message_post_with_template(
                 mail_template.id,
                 composition_mode='comment',
                 email_layout_xmlid='mail.mail_notification_layout_with_responsible_signature',