add balance entity

app/controllers/admin/balances_controller.rb

@@ -0,0 +1,5 @@
+# frozen_string_literal: true
+module Admin
+  class BalancesController < Admin::ApplicationController
+  end
+end

app/controllers/admin/currencies_controller.rb

@@ -1,5 +1,8 @@
 # frozen_string_literal: true
 module Admin
   class CurrenciesController < Admin::ApplicationController
+    def valid_action?(name, resource = resource_class)
+      ["new", "edit", "destroy"].exclude?(name.to_s) && super
+    end
   end
 end