The code is based on what's generated using CKEditor's code generator.
We're doing one minor change to the `Ckeditor::Backend::ActiveStorage`
module; we're assigning the data in a `before_validation` instead of a
`before_save` callback. Validations with `file_validations` didn't work
otherwise; it looks like this backend was written with
`active_storage_validations` in mind [1].
Note we don't need to update the `name` column in the attachments table
because, when using Active Storage, CKEditor uses both `data` (as
attribute accessor) and `storage_data` (as attachment attribute).
[1] https://github.com/galetahub/ckeditor/blob/f9e48420ccb6dc/lib/generators/ckeditor/templates/active_record/active_storage/ckeditor/picture.rb#L4
8c82ff290b