jobs: switch from DelayedJob to GoodJob.

Switch the ActiveJob backend from DelayedJob to GoodJob. Differences:

* The job worker is run with `bin/good_job start` instead of `bin/delayed_job`.
* Jobs have an 8 hour timeout instead of a 4 hour timeout.
* Jobs don't automatically retry on failure.
* Finishing jobs are preserved and pruned after 7 days.

config/environments/production.rb

@@ -45,7 +45,7 @@ Rails.application.configure do
   # config.cache_store = :mem_cache_store
 
   # Use a real queuing backend for Active Job (and separate queues per environment).
-  config.active_job.queue_adapter = :delayed_job
+  config.active_job.queue_adapter = :good_job
   # config.active_job.queue_name_prefix = "danbooru_production"
 
   config.action_mailer.perform_caching = false