Subscribe the user to the newsletter when placing an order with auto-registration?

Question

1C-Bitrix

There is such a code, it works during normal registration, but I can’t figure out how to do the same when registering through an order?

AddEventHandler("main", "OnAfterUserAdd", "OnAfterUserAddHandler");

function OnAfterUserAddHandler(&$arFields)
{

   $errors = Array();

   if($arFields["ID"]>0 && $arFields["UF_SUBSCRIBE"])
   {

      if(CModule::IncludeModule("subscribe")) {
      
         $USER_ID = $arFields["ID"];
         $EMAIL = $arFields["EMAIL"];
      
         $arFilter = array(
            "ACTIVE" => "Y",
            "LID" => "s1",
            "VISIBLE"=>"Y",
         );
      
         $rsRubrics = CRubric::GetList(array(), $arFilter);
         $arRubrics = array();
         while($arRubric = $rsRubrics->GetNext()) $arRubrics[] = $arRubric["ID"];
      
         $obSubscription = new CSubscription;
      
         $rsSubscription = $obSubscription->GetList(array(), array("USER_ID" => $USER_ID));
         $arSubscription = $rsSubscription->Fetch();
   
         if(is_array($arSubscription))
         {
            $rs = $obSubscription->Update(
               $arSubscription["ID"],
               array(
                  "FORMAT" => "html",
                  "RUB_ID" => $arRubrics,
               ),
               false
            );
         }
         else
         {
            $ID = $obSubscription->Add(array(
               "USER_ID" => $USER_ID,
               "ACTIVE" => "Y",
               "EMAIL" => $EMAIL,
               "FORMAT" => "html",
               "CONFIRMED" => "Y",
               "SEND_CONFIRM" => "N",
               "RUB_ID" => $arRubrics,
            ));
         }
      
      }     
   }
}

There is a suspicion that you need to add a custom user field when placing an order