Chore(config): Stop respecting old configuration

`Spree::Config#redirect_back_on_unauthorized` has been removed in
Solidus 3.0, and we're on 4.4 now. This can all go.

If users have followed the deprecation warnings, then they should be
fine with using `redirect_back`.

Note that we're not using redirect_back in the admin, as logging out
redirects to the admin root controller, which in turn redirects back,
leading to an infinite redirect. Infinite redirects are no good.

Author: mamhoff

Diff for: lib/spree/auth/engine.rb

@@ -28,65 +28,30 @@ class Engine < Rails::Engine
         ApplicationController.include Spree::AuthenticationHelpers
       end
 
-      def self.redirect_back_on_unauthorized?
-        return false unless Spree::Config.respond_to?(:redirect_back_on_unauthorized)
-
-        if Spree::Config.redirect_back_on_unauthorized
-          true
-        else
-          Spree::Deprecation.warn <<-WARN.strip_heredoc, caller
-            Having Spree::Config.redirect_back_on_unauthorized set
-            to `false` is deprecated and will not be supported in Solidus 3.0.
-            Please change this configuration to `true` and be sure that your
-            application does not break trying to redirect back when there is
-            an unauthorized access.
-          WARN
-
-          false
-        end
-      end
-
       def self.prepare_backend
         Spree::Admin::BaseController.unauthorized_redirect = -> do
           if spree_current_user
             flash[:error] = I18n.t('spree.authorization_failure')
 
-            if Spree::Auth::Engine.redirect_back_on_unauthorized?
-              redirect_back(fallback_location: spree.admin_unauthorized_path)
-            else
-              redirect_to spree.admin_unauthorized_path
-            end
+            redirect_to(spree.admin_unauthorized_path)
           else
             store_location
 
-            if Spree::Auth::Engine.redirect_back_on_unauthorized?
-              redirect_back(fallback_location: spree.admin_login_path)
-            else
-              redirect_to spree.admin_login_path
-            end
+            redirect_to(spree.admin_login_path)
           end
         end
       end
 
-
       def self.prepare_frontend
         Spree::BaseController.unauthorized_redirect = -> do
           if spree_current_user
             flash[:error] = I18n.t('spree.authorization_failure')
 
-            if Spree::Auth::Engine.redirect_back_on_unauthorized?
-              redirect_back(fallback_location: spree.unauthorized_path)
-            else
-              redirect_to spree.unauthorized_path
-            end
+            redirect_back(fallback_location: spree.unauthorized_path)
           else
             store_location
 
-            if Spree::Auth::Engine.redirect_back_on_unauthorized?
-              redirect_back(fallback_location: spree.login_path)
-            else
-              redirect_to spree.login_path
-            end
+            redirect_back(fallback_location: spree.login_path)
           end
         end
       end

Diff for: spec/controllers/spree/admin/base_controller_spec.rb

@@ -8,10 +8,6 @@
       def index; authorize!(:read, :something); end
     end
 
-    before do
-      stub_spree_preferences(Spree::Config, redirect_back_on_unauthorized: true)
-    end
-
     context "when user is logged in" do
       before { sign_in(create(:user)) }
 
@@ -21,15 +17,6 @@ def index; authorize!(:read, :something); end
           expect(response).to redirect_to(spree.admin_unauthorized_path)
         end
       end
-
-      context "when http_referrer is present" do
-        before { request.env['HTTP_REFERER'] = '/redirect' }
-
-        it "redirects back" do
-          get :index
-          expect(response).to redirect_to('/redirect')
-        end
-      end
     end
 
     context "when user is not logged in" do
@@ -39,15 +26,6 @@ def index; authorize!(:read, :something); end
           expect(response).to redirect_to(spree.admin_login_path)
         end
       end
-
-      context "when http_referrer is present" do
-        before { request.env['HTTP_REFERER'] = '/redirect' }
-
-        it "redirects back" do
-          get :index
-          expect(response).to redirect_to('/redirect')
-        end
-      end
     end
   end
 end

Diff for: spec/controllers/spree/base_controller_spec.rb

@@ -8,10 +8,6 @@
       def index; authorize!(:read, :something); end
     end
 
-    before do
-      stub_spree_preferences(Spree::Config, redirect_back_on_unauthorized: true)
-    end
-
     context "when user is logged in" do
       before { sign_in(create(:user)) }