Merge branch 'emails-on-push-use-sidekiq-mailers' into 'master'

Make EmailsOnPushWorker use Sidekiq mailers queue

A customer was having issues with EmailsOnPushWorker clogging the Sidekiq queues and merge requests not being handled quickly. While researching whether it would possible to spin up a separate Sidekiq task just to handle merge requests and other key functions, I found that this worker was using the default Sidekiq queue. Moving to the `mailers` queue makes it possible to de-prioritize this worker and give more weight to the others.

See merge request !4390

CHANGELOG

@@ -2,6 +2,7 @@ Please view this file on the master branch, on stable branches it's out of date.
 
 v 8.9.0 (unreleased)
   - Allow enabling wiki page events from Webhook management UI
+  - Make EmailsOnPushWorker use Sidekiq mailers queue
   - Fix wiki page events' webhook to point to the wiki repository
   - Allow forking projects with restricted visibility level
   - Improve note validation to prevent errors when creating invalid note via API

app/workers/emails_on_push_worker.rb

 class EmailsOnPushWorker
   include Sidekiq::Worker
 
+  sidekiq_options queue: :mailers
   attr_reader :email, :skip_premailer
 
   def perform(project_id, recipients, push_data, options = {})