DEV: Replace 'processed' column on notifications with new table (#11864)

app/models/shelved_notification.rb

@@ -0,0 +1,9 @@
+# frozen_string_literal: true
+
+class ShelvedNotification < ActiveRecord::Base
+  belongs_to :notification
+
+  def process
+    NotificationEmailer.process_notification(notification, no_delay: true)
+  end
+end