Move e-mail digest task to sidekiq, reduce workload, improve hint (#6252)

app/workers/scheduler/email_scheduler.rb

@@ -0,0 +1,24 @@
+# frozen_string_literal: true
+require 'sidekiq-scheduler'
+
+class Scheduler::EmailScheduler
+  include Sidekiq::Worker
+
+  def perform
+    eligible_users.find_each do |user|
+      next unless user.allows_digest_emails?
+      DigestMailerWorker.perform_async(user.id)
+    end
+  end
+
+  private
+
+  def eligible_users
+    User.confirmed
+        .joins(:account)
+        .where(accounts: { silenced: false, suspended: false })
+        .where(disabled: false)
+        .where('current_sign_in_at < ?', 20.days.ago)
+        .where('last_emailed_at IS NULL OR last_emailed_at < ?', 20.days.ago)
+  end
+end