Add rails-settings-cached, use for initial feature flags

app/controllers/admin/lightning_controller.rb

@@ -13,7 +13,7 @@ class Admin::LightningController < Admin::BaseController
   end
 
   def check_feature_enabled
-    if ENV["LNDHUB_ADMIN_UI"].empty?
+    if !Setting.lndhub_admin_enabled?
       flash[:alert] = "Lightning Admin UI not enabled"
       redirect_to admin_root_path and return
     end