refactory: Whatsapp Notification scheduler events must be setted on hook.py

[HarryPaulo]

Problem: Every time you run migrate, the events inserted in the Scheduled Job Type doctype are deleted.

Reference frappe code:
https://github.com/frappe/frappe/blob/59309f8164f6a360017004324495f456844a49ce/frappe/migrate.py#L141

Frappe limitation:
Currently, the Frappe structure only allows you to create dynamic events for server scripts...

All other events must be in the application's hooks.py, otherwise they will be deleted on run migrate

[HarryPaulo]

A second alternative would be to use the hooks.py event "after_migrate" inserting the events accordingly...

However, the downside of this is that every time you run migrate, frappe will delete the frappe_whatsapp records from the "Scheduled Job Type"

And after migrate ("after_migrate") we would insert a new record in the "Scheduled Job Type".

The downside is the workload when running migrate and the loss of the event execution history.

So this led me to choose to use the system's native trigger "scheduler_events"