[FIX] snailmail: avoid resending letters on rollback

Up until now, the cron would send letters by batch on a single call with
15 secs timeout which is unfortunately insufficient to have an answer
from the IAP server.
The cron would therefore fail and would end up trying to resend the same
letters again and again even if each call had reached the IAP server and that the
letters were actually processed.

closes odoo#55717

Signed-off-by: Rémi Rahir (rar) <[email protected]>

addons/snailmail/models/snailmail_letter.py

@@ -282,7 +282,9 @@ def _snailmail_print(self):
 
     @api.multi
     def snailmail_print(self):
-        self._snailmail_print()
+        self.write({'state': 'pending'})
+        if len(self) == 1:
+            self._snailmail_print()
 
     @api.multi
     def cancel(self):
@@ -297,10 +299,13 @@ def _snailmail_estimate(self):
         return len(self)
 
     @api.model
-    def _snailmail_cron(self):
+    def _snailmail_cron(self, autocommit=True):
         letters_send = self.search([('state', '=', 'pending')])
-        if letters_send:
-            letters_send._snailmail_print()
+        for letter in letters_send:
+            letter._snailmail_print()
+            # Commit after every letter sent to avoid to send it back in case of a rollback
+            if autocommit:
+                self.env.cr.commit()
         limit_date = datetime.datetime.utcnow() - datetime.timedelta(days=1)
         limit_date_str = datetime.datetime.strftime(limit_date, tools.DEFAULT_SERVER_DATETIME_FORMAT)
         letters_canceled = self.search([