use signed uuid in previews

config/initializers/active_storage.rb

@@ -5,6 +5,10 @@ ActiveSupport.on_load(:active_storage_attachment) do
 
   has_many_attached :preview_images
 
+  def signed_uuid
+    @signed_uuid ||= ApplicationRecord.signed_id_verifier.generate(uuid, expires_in: 6.hours)
+  end
+
   def preview_image_url
     preview_images.joins(:blob).find_by(blob: { filename: '0.jpg' })&.url
   end

config/routes.rb

@@ -81,7 +81,7 @@ Rails.application.routes.draw do
     resource :code_modal, only: %i[show], controller: 'templates_code_modal'
     resources :submissions_export, only: %i[index new]
   end
-  resources :preview_document_page, only: %i[show], path: '/preview/:attachment_uuid'
+  resources :preview_document_page, only: %i[show], path: '/preview/:signed_uuid'
 
   resources :start_form, only: %i[show update], path: 'd', param: 'slug' do
     get :completed