We had inconsistent indentation in many places. Now we're fixing them
and adding a linter to our CI so we don't accidentally introduce
inconsistent indentations again.
Using the `document` or `documents` classes meant styles defined for the
public list of documents conflict with these ones.
So now we're using HTML classes that match the name of the Ruby
component classes, as we usually do.
This way we fix a bug we mentioned in commit 930bb753c which caused
links to documents to be broken when editing their title because the
title was used to generate the URL of the document.
Note we're still using Paperclip to render cached attachments because
this is the only case where we store files with just Paperclip and not
Active Storage.
With Active Storage, we render attachments just like any other resource,
using `polymorphic_path`. Paperclip included the `url` method in the
model; since the model doesn't have access to the request parameters
(like the host), this was inconvenient because it wasn't possible to
generate absolute URLs with Paperclip.
In order to simplify the code and make it similar to the way we used
Paperclip, we're adding a `variant` method accepting the name of a
variant and returning the variant.
