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.
Using `<a>` tags with no `href` means these elements cannot be activated
by keyboard users, so we're replacing them with buttons.
In the future we probably want to add more consistency so all toggle
buttons use the same code. We might also add styles depending on the
`aria-expanded` property.
Note this rule does still allow us to add new lines after opening tags;
it just makes sure that if we do, we also add it in closing tags.
Likewise, if we don't add it in the opening tag, it forces us not to add
it in the closing tag either.
I don't have a strong preference about either style; in these cases I've
chosen the latter because it seemed more common in our code.
