Fix code duplication for merge/personalization feature
Created by: racke
Same block of code appears four times in `Sympa::Spindle::AuthorizeMessage which is a violation of the DRY rule.
# Check syntax for merge_feature.
if ( $message->{shelved}{merge}
and $message->{shelved}{merge} ne 'footer'
and not _test_personalize($message, $list)) {
$log->syslog(
'err',
'Failed to personalize. Message %s for list %s was rejected',
$message,
$list
);
Sympa::send_dsn($list, $message, {}, '5.6.5');
return undef;
}