chore: add the attachment resource as a demo

spec/dummy/app/avo/resources/attachment_resource.rb

@@ -0,0 +1,9 @@
+class AttachmentResource < Avo::BaseResource
+  self.title = :filename
+  self.model_class = "ActiveStorage::Attachment"
+
+  field :id, as: :id
+  field :filename, as: :text
+  field :service_url, as: :external_image, name: "Image"
+  field :created_at, as: :date_time
+end

spec/dummy/app/avo/resources/post_resource.rb

@@ -42,6 +42,8 @@ class PostResource < Avo::BaseResource
     extract_excerpt model.body
   end
 
+  field :cover_photo_attachment, as: :has_one
+
   field :is_featured, as: :boolean, visible: ->(resource:) { context[:user].is_admin? }
   field :is_published, as: :boolean do |model|
     model.published_at.present?

spec/dummy/app/avo/resources/project_resource.rb

@@ -35,6 +35,8 @@ class ProjectResource < Avo::BaseResource
   field :comments, as: :has_many, searchable: true
   field :reviews, as: :has_many
 
+  field :files_attachments, as: :has_many
+
   action ExportCsv
 
   # filter PeopleFilter

spec/dummy/app/controllers/avo/attachments_controller.rb

@@ -0,0 +1,4 @@
+# This controller has been generated to enable Rails' resource routes.
+# More information on https://docs.avohq.io/2.0/controllers.html
+class Avo::AttachmentsController < Avo::ResourcesController
+end