* Add new UpdateMainImageBackgroundHexWorker worker class
This is a port of app/jobs/update_main_image_background_job.rb
that works with Sidekiq instead of DelayedJob.
* Update all references to UpdateMainImageBackgroundHexJob
This updates all references to UpdateMainImageBackgroundHexJob
so they now call UpdateMainImageBackgroundHexWorker, which works
with Sidekiq instead of DelayedJob.
* Move method call to after_commit callback
* Fix article specs with sidekiq helpers
Co-authored-by: Alex <alexandersmith223@gmail.com>