ラインアイテムの数量を調整可能にする

const session = await stripe.checkout.sessions.create({
  line_items: [
    {
      price_data: {
        currency: 'usd',
        product_data: {
          name: 'T-shirt',
        },
        unit_amount: 2000,
      },
      quantity: 1,
      adjustable_quantity: {
        enabled: true,
        maximum: 100,
        minimum: 0,
      },
    },
  ],
  mode: 'payment',
  ui_mode: 'custom',
  return_url: '{{RETURN_URL}}'
});

# Set your secret key. Remember to switch to your live secret key in production!
# See your keys here: https://dashboard.stripe.com/apikeys
Stripe.api_key = 
"sk_test_BQokikJOvBiI2HlWgH4olfQ2"

require 'sinatra'

# You can find your endpoint's secret in your webhook settings
endpoint_secret = 'whsec_...'

post '/webhook' do
  event = nil

  # Verify webhook signature and extract the event
  # See https://stripe.com/docs/webhooks#verify-events for more information.
  begin
    sig_header = request.env['HTTP_STRIPE_SIGNATURE']
    payload = request.body.read
    event = Stripe::Webhook.construct_event(payload, sig_header, endpoint_secret)
  rescue JSON::ParserError => e
    # Invalid payload
    return status 400
  rescue Stripe::SignatureVerificationError => e
    # Invalid signature
    return status 400
  end

  if event['type'] == 'checkout.session.completed'
    checkout_session = event['data']['object']

    line_items = Stripe::Checkout::Session.list_line_items(checkout_session['id'], {limit: 100})

    # Fulfill the purchase...
    begin
      fulfill_order(checkout_session, line_items)
    rescue NotImplementedError => e
      return status 400
    end
  end

  status 200
end

def fulfill_order(checkout_session, line_items)
  # TODO: Remove error and implement...
  raise NotImplementedError.new(<<~MSG)
    Given the Checkout Session "#{checkout_session.id}" load your internal order from the database here.
    Then you can reconcile your order's quantities with the final line item quantity purchased. You can use `checkout_session.metadata` and `price.metadata` to store and later reference your internal order and item ids.
  MSG
end