async photo uploading

controller.rb

def upload_photo
  event = Event.find(params[:event_id])
  params.delete(:event_id)
  icon = EventIcon.create(params)
  # This requires setting up a many-to-one relationship between icons and events
  event.icons << icon
  event.save!
  render json: {
    id: icon.id,
    name: icon.photo_file_name,
    url: icon.photo.url
  }
end