Folio::HasSanitizedFields modify to add new fields to inherited

Eg.: 
Folio have
```
class Folio::User < Folio::ApplicationRecord
  has_sanitized_fields :email, :first_name, :last_name, :company_name, :nickname

end
```

app do Folio::User override as:
```
Folio::User.class_eval do
  has_sanitized_fields :organization_name

end

```

result  => only `:organizational_name` is sanitized.

