invoice.pdf.url(expires_in: 15.minutes, disposition: :attachment)

  # config/initializers/active_storage.rb
  Rails.application.config.active_storage.service_urls_expire_in = 15.minutes

  # Proxied through your app — revocable, but every byte goes through Rails
  rails_blob_url(invoice.pdf, disposition: :attachment)
  url_for(invoice.pdf)

  # Direct to the storage service — fast, not revocable before expiry
  invoice.pdf.url(expires_in: 15.minutes, disposition: :attachment)

  # Control the downloaded filename
  invoice.pdf.url(
    expires_in: 5.minutes,
    disposition: :attachment,
    filename: ActiveStorage::Filename.new("invoice-#{invoice.number}.pdf")
  )

  # Variants of an image
  user.avatar.variant(resize_to_limit: [200, 200]).processed.url(expires_in: 1.hour)

  # Authorize FIRST — the signature says nothing about who is asking
  class InvoicesController < ApplicationController
    def download
      invoice = current_account.invoices.find(params[:id])
      redirect_to invoice.pdf.url(expires_in: 5.minutes, disposition: :attachment),
                  allow_other_host: true
    end
  end