Enhance SolidusAdmin authorization with improved redirect mechanism

In scenarios where a user attempts to access a resource, they are not authorized
to access, we now handle this by redirecting them to the old admin dashboard
as a fallback.

This approach serves as an interim solution. As we advance in decoupling the
new admin from the old one, we'll reassess and adjust this redirect method
to align better with the new system's structure.

admin/app/controllers/solidus_admin/controller_helpers/authorization.rb

@@ -18,6 +18,8 @@ def authorize_solidus_admin_user!
 
     authorize! :admin, subject
     authorize! action_name.to_sym, subject
+  rescue CanCan::AccessDenied
+    instance_exec(&Spree::Admin::BaseController.unauthorized_redirect)
   end
 
   def authorization_subject

admin/spec/controllers/solidus_admin/base_controller_spec.rb

@@ -15,10 +15,22 @@ def index
       allow_any_instance_of(SolidusAdmin::BaseController).to receive(:spree_current_user).and_return(nil)
     end
 
-    it "redirects to unauthorized" do
+    it "redirects to unauthorized for no user" do
       get :index
       expect(response).to redirect_to '/unauthorized'
     end
+
+    context "with a user without update permission" do
+      before do
+        user = create(:user, email: '[email protected]')
+        allow_any_instance_of(SolidusAdmin::BaseController).to receive(:spree_current_user).and_return(user)
+      end
+
+      it "redirects to unauthorized" do
+        get :index
+        expect(response).to redirect_to '/unauthorized'
+      end
+    end
   end
 
   context "successful request" do