invites: Add durable=True to transaction in do_invite_users.

This commit adds 'durable=True' to the outermost transaction
in 'do_invite_users'.

It also adds 'savepoint=False' to inner transaction.atomic
decorators to avoid creating savepoints.

zerver/actions/invites.py

@@ -173,7 +173,7 @@ def check_invite_limit(realm: Realm, num_invitees: int) -> None:
             )
 
 
-@transaction.atomic
+@transaction.atomic(durable=True)
 def do_invite_users(
     user_profile: UserProfile,
     invitee_emails: Collection[str],
@@ -414,7 +414,7 @@ def do_revoke_multi_use_invite(multiuse_invite: MultiuseInvite) -> None:
     notify_invites_changed(realm, changed_invite_referrer=multiuse_invite.referred_by)
 
 
-@transaction.atomic
+@transaction.atomic(savepoint=False)
 def do_send_user_invite_email(
     prereg_user: PreregistrationUser,
     *,

zerver/lib/send_email.py

@@ -378,7 +378,7 @@ def send_future_email(
         # For logging the email
 
     assert (to_user_ids is None) ^ (to_emails is None)
-    with transaction.atomic():
+    with transaction.atomic(savepoint=False):
         email = ScheduledEmail.objects.create(
             type=EMAIL_TYPES[template_name],
             scheduled_timestamp=timezone_now() + delay,