NOTE: we semi-enforce using the OrderLog_Controller here to deal with the submission of the OrderStatusLogForm You can use your own Logs or an extension of OrderLog_Controller by setting the first parameter (optionalController) to your own controller.
Signature
public function __construct([Controller
$optionalController = NULL,
string
$name,
FieldList
$fields,
FieldList
$actions,
[Validator
$optionalValidator = NULL]] )