Split ConfirmOrderJob to avoid blocking a worker

This unties this two email notifications so that they are picked up by
a DJ worker independently. This should avoid the blocking the worker experiences (remember we
still have a single one in all instances) when waiting between the two
deliveries. See the flamegraph:
https://app.datadoghq.com/apm/traces?end=1622015605459&paused=true&query=env%3Aproduction%20service%3Adelayed_job%20operation_name%3Adelayed_job%20resource_name%3AConfirmOrderJob%20%40duration%3A%3E%3D5s&start=1622009898303&streamTraces=true&trace=AQAAAXmngbg_woqc_QAAAABBWG1uZ2IwVkFBRHVDbWJkN25QTUVuY28&traceID=2916038355421570548&spanID=2005781139590273685.

Overall, both operations may take longer but other jobs can be processed
in between. Also, if any of the two fails, the other won't be affected.

app/jobs/confirm_order_job.rb

@@ -1,8 +0,0 @@
-# frozen_string_literal: true
-
-class ConfirmOrderJob < ActiveJob::Base
-  def perform(order_id)
-    Spree::OrderMailer.confirm_email_for_customer(order_id).deliver_now
-    Spree::OrderMailer.confirm_email_for_shop(order_id).deliver_now
-  end
-end

app/models/spree/order.rb

@@ -395,7 +395,8 @@ module Spree
     def deliver_order_confirmation_email
       return if subscription.present?
 
-      ConfirmOrderJob.perform_later(id)
+      Spree::OrderMailer.confirm_email_for_customer(id).deliver_later
+      Spree::OrderMailer.confirm_email_for_shop(id).deliver_later
     end
 
     # Helper methods for checkout steps

spec/features/consumer/shopping/checkout_spec.rb

@@ -251,10 +251,14 @@ feature "As a consumer I want to check out my cart", js: true do
         choose shipping_with_fee.name
         choose check_without_fee.name
 
-        expect do
+        perform_enqueued_jobs do
           place_order
+
           expect(page).to have_content "Your order has been processed successfully"
-        end.to enqueue_job ConfirmOrderJob
+
+          expect(ActionMailer::Base.deliveries.first.subject).to match(/Order Confirmation/)
+          expect(ActionMailer::Base.deliveries.second.subject).to match(/Order Confirmation/)
+        end
 
         order = Spree::Order.complete.last
         expect(order.payment_state).to eq "balance_due"
@@ -390,7 +394,7 @@ feature "As a consumer I want to check out my cart", js: true do
         expect do
           place_order
           expect(page).to have_content "Your order has been processed successfully"
-        end.to enqueue_job ConfirmOrderJob
+        end.to have_enqueued_mail(Spree::OrderMailer, :confirm_email_for_customer)
 
         # And the order's special instructions should be set
         order = Spree::Order.complete.last

spec/jobs/confirm_order_job_spec.rb

@@ -1,18 +0,0 @@
-# frozen_string_literal: true
-
-require 'spec_helper'
-
-describe ConfirmOrderJob do
-  let(:order) { create(:order) }
-
-  it "sends confirmation emails to both the user and the shop owner" do
-    customer_confirm_fake = double(:confirm_email_for_customer)
-    shop_confirm_fake = double(:confirm_email_for_shop)
-    expect(Spree::OrderMailer).to receive(:confirm_email_for_customer).and_return customer_confirm_fake
-    expect(Spree::OrderMailer).to receive(:confirm_email_for_shop).and_return shop_confirm_fake
-    expect(customer_confirm_fake).to receive :deliver_now
-    expect(shop_confirm_fake).to receive :deliver_now
-
-    ConfirmOrderJob.perform_now order.id
-  end
-end

spec/jobs/subscription_confirm_job_spec.rb

@@ -237,7 +237,9 @@ describe SubscriptionConfirmJob do
           end
 
           it "sends only a subscription confirm email, no regular confirmation emails" do
-            expect{ job.send(:confirm_order!, order) }.to_not enqueue_job ConfirmOrderJob
+            expect{ job.send(:confirm_order!, order) }
+              .to_not have_enqueued_mail(Spree::OrderMailer, :confirm_email_for_customer)
+
             expect(job).to have_received(:send_confirmation_email).once
           end
         end

spec/jobs/subscription_placement_job_spec.rb

@@ -202,7 +202,9 @@ describe SubscriptionPlacementJob do
         end
 
         it "does not enqueue confirmation emails" do
-          expect{ job.send(:place_order, order) }.to_not enqueue_job ConfirmOrderJob
+          expect{ job.send(:place_order, order) }
+              .to_not have_enqueued_mail(Spree::OrderMailer, :confirm_email_for_customer)
+
           expect(job).to have_received(:send_placement_email).with(order, anything).once
         end
 

spec/models/spree/order_spec.rb

@@ -169,10 +169,13 @@ describe Spree::Order do
       expect(order.shipment_state).to eq 'ready'
     end
 
-    it "should send an order confirmation email" do
-      expect do
-        order.finalize!
-      end.to enqueue_job ConfirmOrderJob
+    it "sends confirmation emails to both the user and the shop owner" do
+      mailer = double(:mailer, deliver_later: true)
+
+      expect(Spree::OrderMailer).to receive(:confirm_email_for_customer).and_return(mailer)
+      expect(Spree::OrderMailer).to receive(:confirm_email_for_shop).and_return(mailer)
+
+      order.finalize!
     end
 
     it "should freeze all adjustments" do
@@ -901,17 +904,20 @@ describe Spree::Order do
     let!(:order) { create(:order, distributor: distributor) }
 
     it "sends confirmation emails" do
-      expect do
-        order.deliver_order_confirmation_email
-      end.to enqueue_job ConfirmOrderJob
+      mailer = double(:mailer, deliver_later: true)
+      expect(Spree::OrderMailer).to receive(:confirm_email_for_customer).and_return(mailer)
+      expect(Spree::OrderMailer).to receive(:confirm_email_for_shop).and_return(mailer)
+
+      order.deliver_order_confirmation_email
     end
 
     it "does not send confirmation emails when the order belongs to a subscription" do
       create(:proxy_order, order: order)
 
-      expect do
-        order.deliver_order_confirmation_email
-      end.to_not enqueue_job ConfirmOrderJob
+      expect(Spree::OrderMailer).not_to receive(:confirm_email_for_customer)
+      expect(Spree::OrderMailer).not_to receive(:confirm_email_for_shop)
+
+      order.deliver_order_confirmation_email
     end
   end