Ensure all Job classes correctly inherit from ActiveJob

app/jobs/heartbeat_job.rb

@@ -1,4 +1,6 @@
-class HeartbeatJob
+# frozen_string_literal: true
+
+class HeartbeatJob < ActiveJob::Base
   def perform
     Spree::Config.last_job_queue_heartbeat_at = Time.now.in_time_zone
   end

app/jobs/manager_invitation_job.rb

@@ -1,5 +1,7 @@
-ManagerInvitationJob = Struct.new(:enterprise_id, :user_id) do
-  def perform
+# frozen_string_literal: true
+
+class ManagerInvitationJob < ActiveJob::Base
+  def perform(enterprise_id, user_id)
     enterprise = Enterprise.find enterprise_id
     user = Spree::User.find user_id
     EnterpriseMailer.manager_invitation(enterprise, user).deliver_now

app/jobs/subscription_confirm_job.rb

@@ -1,7 +1,7 @@
 require 'order_management/subscriptions/summarizer'
 
 # Confirms orders of unconfirmed proxy orders in recently closed Order Cycles
-class SubscriptionConfirmJob
+class SubscriptionConfirmJob < ActiveJob::Base
   def perform
     confirm_proxy_orders!
   end

app/jobs/subscription_placement_job.rb

@@ -1,6 +1,6 @@
 require 'order_management/subscriptions/summarizer'
 
-class SubscriptionPlacementJob
+class SubscriptionPlacementJob < ActiveJob::Base
   def perform
     ids = proxy_orders.pluck(:id)
     proxy_orders.update_all(placed_at: Time.zone.now)