model validations and update callbacks

[Hellfar]

In this type of model files:
https://github.com/foundpatterns/send-file-package/blob/master/models/slide.yaml

Validation fields:
It would be nice to handle fields validations such as (for example):

• Presence;
• Range;
• emptiness;
• string fitting pattern;
• ....

Callbacks events:
It would be also nice to define the name of callbacks to call when an item is created or updated or etc...

For example:

fields:
  title:
    type: string
    validation:
      presence: true
  body:
    type: string
    on_create: on_create_my_method

on_create_my_method which is a method defined somewhere by the user of the framework.

Those features in Rails are named Active model and is documented in:
https://guides.rubyonrails.org/active_model_basics.html#model