[FIX] purchase: join() result is not Markup object

When Markup objects are joined by a str, the result will be a str.
So, here:
https://github.com/odoo/odoo/blob/5f3db6683ab191cb68af4c8d6bb2e86a5b114ee1/addons/purchase/models/account_invoice.py#L137
altought refs is all markup objects, join will return a normal str
object that will be escaped.
To fix, we join them by markup object.

closes odoo/odoo#122268

X-original-commit: cc4a50091e540ddcc8b46ee77277bd53e634d536
Signed-off-by: Steve Van Essche <svs@odoo.com>

addons/purchase/models/account_invoice.py

@@ -3,7 +3,7 @@
 import difflib
 import logging
 import time
-from markupsafe import escape
+from markupsafe import Markup
 
 from odoo import api, fields, models, Command, _
 
@@ -134,7 +134,7 @@ class AccountMove(models.Model):
             if not purchases:
                 continue
             refs = [purchase._get_html_link() for purchase in purchases]
-            message = escape(_("This vendor bill has been created from: %s")) % ','.join(refs)
+            message = _("This vendor bill has been created from: ") + Markup(',').join(refs)
             move.message_post(body=message)
         return moves
 
@@ -149,7 +149,7 @@ class AccountMove(models.Model):
             diff_purchases = new_purchases - old_purchases[i]
             if diff_purchases:
                 refs = [purchase._get_html_link() for purchase in diff_purchases]
-                message = escape(_("This vendor bill has been modified from: %s")) % ','.join(refs)
+                message = _("This vendor bill has been modified from: ") + Markup(',').join(refs)
                 move.message_post(body=message)
         return res