[IMP] snailmail: Only resend concerned letter from format error

Previously, when updating and resending a snailmail through the chatter,
it would re-send every snailmail letters in the DB with an error.

This behaviour lead to users mistakenly sending dozens of unwanted
snailmails, expecting to re-send the one they were currently on.

This commit changes that by only sending the relevant letter(s).

closes odoo/odoo#146078

X-original-commit: 43a56e84919604608d12bf3d8528339733fc79d8
Signed-off-by: Louis Baudoux (lba) <lba@odoo.com>
Signed-off-by: Solan Delvenne (sode) <sode@odoo.com>

addons/snailmail/wizard/snailmail_letter_format_error.py

@@ -1,4 +1,3 @@
-
 from odoo import api, fields, models
 
 class SnailmailLetterFormatError(models.TransientModel):
@@ -16,9 +15,7 @@ class SnailmailLetterFormatError(models.TransientModel):
 
     def update_resend_action(self):
         self.env.company.write({'snailmail_cover': self.snailmail_cover})
-        letters_to_resend = self.env['snailmail.letter'].search([
-            ('error_code', '=', 'FORMAT_ERROR'),
-        ])
+        letters_to_resend = self.message_id.letter_ids
         for letter in letters_to_resend:
             old_attachment = letter.attachment_id
             letter.attachment_id = False