[FIX] snailmail: dont resend without credits

We are spammed by some accounts that don't have credits anymore.

With this commit, when we try to send letters from the cron, whenever we
meet the CREDIT_ERROR error_code, we stop trying to send the letter.

task-2930455

closes odoo/odoo#103489

X-original-commit: f1fed40e
Signed-off-by: Florian Daloze (fda) <fda@odoo.com>

addons/snailmail/models/snailmail_letter.py

@@ -403,6 +403,8 @@ class SnailmailLetter(models.Model):
         ])
         for letter in letters_send:
             letter._snailmail_print()
+            if letter.error_code == 'CREDIT_ERROR':
+                break  # avoid spam
             # Commit after every letter sent to avoid to send it again in case of a rollback
             if autocommit:
                 self.env.cr.commit()