Use ActiveJob instead of Resque directly

This allows us to directly pass entities to the job.

app/jobs/notify_negative_balance_job.rb

@@ -0,0 +1,11 @@
+class NotifyNegativeBalanceJob < ApplicationJob
+  def perform(ordergroup, transaction)
+    ordergroup.users.each do |user|
+      next unless user.settings.notify['negative_balance']
+
+      Mailer.deliver_now_with_user_locale user do
+        Mailer.negative_balance(user, transaction)
+      end
+    end
+  end
+end