Spree.config do |config|
  config.admin_path = 'backend'
end

Routes for Spree::Core::Engine:
admin_translations GET    /admin/:resource/:resource_id/translations(.:format)                         spree/admin/translations#index
admin_option_type_option_value PATCH  /admin/option_values/:id(.:format)                                           spree/admin/option_values#update
admin_translate_product_property PATCH  /admin/product/:id/product_properties/:id(.:format)                          spree/admin/product_properties#translate
 admin_unauthorized GET    /backend/authorization_failure(.:format)                                      spree/admin/user_sessions#authorization_failure
admin_login GET    /backend/login(.:format)                                                      spree/admin/user_sessions#new