Extract redirection behavior from lambda to classes

We have to lambdas, so we need two classes.

app/models/spree/auth/unauthorized_admin_access_handler.rb

@@ -0,0 +1,33 @@
+# frozen_string_literal: true
+
+module Spree
+  module Auth
+    # This service object is responsible for handling unauthorized redirects
+    class UnauthorizedAdminAccessHandler
+      # @param controller [ApplicationController] an instance of ApplicationController
+      #  or its subclasses.
+      def initialize(controller)
+        @controller = controller
+      end
+
+      # This method is responsible for handling unauthorized redirects
+      def call
+        if spree_current_user
+          flash[:error] = I18n.t('spree.authorization_failure')
+
+          redirect_to(spree.admin_unauthorized_path)
+        else
+          store_location
+
+          redirect_to(spree.admin_login_path)
+        end
+      end
+
+      private
+
+      attr_reader :controller
+
+      delegate :flash, :redirect_to, :spree_current_user, :store_location, :spree, to: :controller
+    end
+  end
+end

app/models/spree/auth/unauthorized_customer_access_handler.rb

@@ -0,0 +1,33 @@
+# frozen_string_literal: true
+
+module Spree
+  module Auth
+    # This service object is responsible for handling unauthorized redirects
+    class UnauthorizedCustomerAccessHandler
+      # @param controller [ApplicationController] an instance of ApplicationController
+      #  or its subclasses.
+      def initialize(controller)
+        @controller = controller
+      end
+
+      # This method is responsible for handling unauthorized redirects
+      def call
+        if spree_current_user
+          flash[:error] = I18n.t('spree.authorization_failure')
+
+          redirect_back(fallback_location: spree.unauthorized_path)
+        else
+          store_location
+
+          redirect_back(fallback_location: spree.login_path)
+        end
+      end
+
+      private
+
+      attr_reader :controller
+
+      delegate :flash, :redirect_back, :spree_current_user, :store_location, :spree, to: :controller
+    end
+  end
+end

lib/spree/auth/engine.rb

@@ -30,29 +30,13 @@ class Engine < Rails::Engine
 
       def self.prepare_backend
         Spree::Admin::BaseController.unauthorized_redirect = -> do
-          if spree_current_user
-            flash[:error] = I18n.t('spree.authorization_failure')
-
-            redirect_to(spree.admin_unauthorized_path)
-          else
-            store_location
-
-            redirect_to(spree.admin_login_path)
-          end
+          Spree::Auth::UnauthorizedAdminAccessHandler.new(self).call
         end
       end
 
       def self.prepare_frontend
         Spree::BaseController.unauthorized_redirect = -> do
-          if spree_current_user
-            flash[:error] = I18n.t('spree.authorization_failure')
-
-            redirect_back(fallback_location: spree.unauthorized_path)
-          else
-            store_location
-
-            redirect_back(fallback_location: spree.login_path)
-          end
+          Spree::Auth::UnauthorizedCustomerAccessHandler.new(self).call
         end
       end
     end