Common migrations look for all models with *_file_name attributes but I
found that unreliable in our code base. It finds too many model classes
and doesn't allow us to be more selective in the migration. So I used
our own migration declaration to migrate exactly those attachments
specified.
Active Storage always touches associated records when attachments are
changed. But for the Terms of Service it's important to keep the
updated_at date because that's how we find out how new it is and if a
customer accepted those terms already.
And while we migrate files, the content of the files will stay the same
and we don't want customers to be asked to accept the same terms again.
We do this for all models in the code base. There's one special case,
the ConentConfiguration which is not a model and we can't use the same
approach there. We will have to deal with that separately later.
I chose `has_one_migrating` as method name for two reasons:
1. It reflects Active Storage's method `has_one_attached`.
2. And it has the same length as Paperclip's `has_attached_file`.
Therefore the commits don't need any whitespace changes.
When we change it to `has_one_attached`, we will also remove the
Paperclip options which then don't need whitespace changes either.
While we migrate from Paperclip to Active Storage, we need to use both
at the same time to avoid any downtime or lost images.
Once the migration is complete, we want to use the same name for
attachment as before. Using Paperclip and Active Storage at the same
time creates a name conflict on a couple of methods.
I'm using alias_method as a temporary solution to access Active Storage
methods. We will remove that after the migration. I declare Paperclip
afterwards so that we have those methods declarations for backwards
compatibility now.
The icons are not used any more and the default icon file never existed
in our code base (only in Spree when we depended on that).
And it's better to remove this clutter before migrating those files to
Active Storage.
We are keeping the icon files in storage as a backup. The whole folder
`/spree/taxons` can be deleted when desired. But storage is cheap.
We had an old version under "contested settings" and it looks like some
of them were modified. I hope that our new, separate file will
discourage manual tweaks.
We can include the relaxed rules from a gem as well. Let's see if we
need that complexity one day.
