docs: add @todo

Author: kenjis

system/Entity/Exceptions/CastException.php

@@ -15,6 +15,10 @@
 
 /**
  * CastException is thrown for invalid cast initialization and management.
+ *
+ * @TODO CodeIgniter\Exceptions\CastException is deprecated and this class is used.
+ *      CodeIgniter\Exceptions\CastException has the property $code = EXIT_CONFIG,
+ *      but this class does not have the code.
  */
 class CastException extends FrameworkException
 {