POC: extract state machines to a concern

core/app/models/spree/return_authorization.rb

@@ -22,13 +22,7 @@ class ReturnAuthorization < Spree::Base
     validate :must_have_shipped_units, on: :create
     validate :no_previously_exchanged_inventory_units, on: :create
 
-    state_machine initial: :authorized do
-      before_transition to: :canceled, do: :cancel_return_items
-
-      event :cancel do
-        transition to: :canceled, from: :authorized, if: lambda { |return_authorization| return_authorization.can_cancel_return_items? }
-      end
-    end
+    include ::Spree::Config.state_machines.return_authorization
 
     extend DisplayMoney
     money_methods :pre_tax_total, :amount, :total_excluding_vat

core/lib/spree/app_configuration.rb

@@ -434,6 +434,10 @@ def order_number_generator
       @order_number_generator ||= Spree::Order::NumberGenerator.new
     end
 
+    def state_machines
+      @state_machines ||= Spree::Core::StateMachines.new
+    end
+
     def static_model_preferences
       @static_model_preferences ||= Spree::Preferences::StaticModelPreferences.new
     end

core/lib/spree/core.rb

@@ -84,6 +84,7 @@ class GatewayError < RuntimeError; end
 require 'spree/core/controller_helpers/store'
 require 'spree/core/controller_helpers/strong_parameters'
 require 'spree/core/role_configuration'
+require 'spree/core/state_machines'
 require 'spree/core/stock_configuration'
 require 'spree/core/validators/email'
 require 'spree/permission_sets'

core/lib/spree/core/state_machines.rb

@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+
+module Spree
+  module Core
+    class StateMachines
+      attr_writer :return_authorization
+
+      def return_authorization
+        require 'spree/core/state_machines/base_return_authorization'
+
+        @return_authorization ||= 'Spree::Core::StateMachines::BaseReturnAuthorization'
+        @return_authorization.constantize
+      end
+    end
+  end
+end

core/lib/spree/core/state_machines/base_return_authorization.rb

@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+
+module Spree
+  module Core
+    class StateMachines
+      module BaseReturnAuthorization
+        extend ActiveSupport::Concern
+
+        included do
+          state_machine initial: :authorized do
+            before_transition to: :canceled, do: :cancel_return_items
+
+            event :cancel do
+              transition to: :canceled, from: :authorized, if: lambda { |return_authorization| return_authorization.can_cancel_return_items? }
+            end
+          end
+        end
+      end
+    end
+  end
+end