Periodically remove expired PuSH subscribers (#4654)

app/workers/scheduler/subscriptions_cleanup_scheduler.rb

@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+require 'sidekiq-scheduler'
+
+class Scheduler::SubscriptionsCleanupScheduler
+  include Sidekiq::Worker
+
+  def perform
+    Subscription.expired.in_batches.delete_all
+  end
+end