Add shortcut to order's exchange

app/jobs/backorder_job.rb

@@ -134,7 +134,6 @@ class BackorderJob < ApplicationJob
         user, order.distributor, order.order_cycle, placed_order.semanticId
       )
 
-    exchange = order.order_cycle.exchanges.outgoing.find_by(receiver: order.distributor)
-    exchange.semantic_links.create!(semantic_id: placed_order.semanticId)
+    order.exchange.semantic_links.create!(semantic_id: placed_order.semanticId)
   end
 end

app/models/spree/order.rb

@@ -67,8 +67,11 @@ module Spree
              class_name: 'Spree::Adjustment',
              dependent: :destroy
     has_many :invoices, dependent: :restrict_with_exception
-
     belongs_to :order_cycle, optional: true
+    has_one :exchange, ->(order) {
+      outgoing.to_enterprise(order.distributor)
+    }, through: :order_cycle, source: :exchanges
+
     belongs_to :distributor, class_name: 'Enterprise', optional: true
     belongs_to :customer, optional: true
     has_one :proxy_order, dependent: :destroy

spec/models/spree/order_spec.rb

@@ -6,6 +6,8 @@ RSpec.describe Spree::Order do
   let(:user) { build(:user, email: "spree@example.com") }
   let(:order) { build(:order, user:) }
 
+  it { is_expected.to have_one :exchange }
+
   describe "#errors" do
     it "provides friendly error messages" do
       order.ship_address = Spree::Address.new