Implement callbacks for Models

Callback Models:

```ruby
[
  :before_validation,
  :around_validation,
  :after_validation,

  :before_save,
  :around_save,
  :after_save,

  :before_create,
  :around_create,
  :after_create,

  :before_update,
  :around_update,
  :after_update,

  :before_destroy,
  :around_destroy,
  :after_destroy
]
```

Each of those takes a symbol, which is the name of the method.