Add end-to-end (system) tests (#25461)

lib/tasks/spec.rake

@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+if Rake::Task.task_defined?('spec:system')
+  namespace :spec do
+    task :enable_system_specs do # rubocop:disable Rails/RakeEnvironment
+      ENV['RUN_SYSTEM_SPECS'] = 'true'
+    end
+  end
+
+  Rake::Task['spec:system'].enhance ['spec:enable_system_specs']
+end