Extract FoiAttachment::Dsn & restore functionality

[garethrees]

What does this do?

Extract FoiAttachment::Dsn & restore functionality

Why was this needed?

The list of DSN codes was constantly getting in the way when viewing foi_attachment.rb. Also, it was doing nothing, so might as well fix it.

Screenshots

BEFORE

AFTER

Notes to reviewer

[gbp]

Great, much better than all being in FoiAttachment.

Tested by sending a mail to the holding pen with:

mail = Mail.new do
  body 'Hello World'
  add_file filename: 'DSN', content: File.read('spec/fixtures/files/attachment.delivery_status'), content_type: 'message/delivery-status'
end
RequestMailer.receive mail.to_s

I guess we could move the em tag into the view which is probably the correct thing to do but happy to leave it as is.

Merge once you're happy.

diff --git a/app/models/foi_attachment.rb b/app/models/foi_attachment.rb
index d1381eb5a..596c37c22 100644
--- a/app/models/foi_attachment.rb
+++ b/app/models/foi_attachment.rb
@@ -164,7 +164,7 @@ def extra_note
     dsn = DeliveryStatusNotification.new(body)
     return unless dsn.status && dsn.message
 
-    "<em>DSN: #{dsn.status} #{dsn.message}</em>".html_safe
+    "DSN: #{dsn.status} #{dsn.message}"
   end
 
   # Called by controller so old filenames still work
diff --git a/app/views/request/_attachments.html.erb b/app/views/request/_attachments.html.erb
index 8022ec812..83dbc48aa 100644
--- a/app/views/request/_attachments.html.erb
+++ b/app/views/request/_attachments.html.erb
@@ -32,7 +32,7 @@
               <% if a.has_body_as_html? && incoming_message.info_request.prominence(:decorate => true).is_public? %>
                 <%= link_to "View as HTML", attachment_path(a, :html => true) %>
               <% end %>
-              <%= a.extra_note %>
+              <% if note = a.extra_note %><em><%= note %></em><% end %>
             </p>
           <% end %>
         <% end %>

[gbp]

Oh. dns.rb is still present

ls app/models/foi_attachment
delivery_status_notification.rb dsn.rb prominence.rb