OTA callback event lifecycle

If you are asking a question, please follow this template:

  1. My goal is: To execute code before the device reboots after a successful OTA
  2. My actions are: Try to look up the Mongoose Event codes for OTA
  3. The result I see is: I can’t find them documented anywhere
  4. My expectation & question is: Does anyone know how to hook into the Mongoose OTA event lifecucle with mgos_event_add_handler() or mgos_event_add_group_handler()?