DEV: Add more debugging context to onebox generation

Previously if a onebox timed out we would not present the users in the log
with any information regarding the onebox. This makes it very difficult to
debug.

This adds url/topic/user in the debugging output.

app/controllers/onebox_controller.rb

@@ -21,7 +21,7 @@ class OneboxController < ApplicationController
 
     return render(body: nil, status: 404) if Oneboxer.recently_failed?(url)
 
-    hijack do
+    hijack(info: "#{url} topic_id: #{topic_id} user_id: #{user_id}") do
       Oneboxer.preview_onebox!(user_id)
 
       preview = Oneboxer.preview(url,