Direct upload

For Rails Active Storage direct upload disk all that is needed is:

# config/importmap.rb
pin "@rails/activestorage", to: "activestorage.esm.js"

// app/javascript/application.js
import * as ActiveStorage from "@rails/activestorage"
ActiveStorage.start()

<%= form.file_field :attachments, multiple: true, direct_upload: true %>