Support for local delivery apps

Added initial support for Zapiet and Bird Chime apps in multi-recipient checkout so merchants can allow for shipping and/or local delivery options for each recipient.

• In the checkout > recipient field settings, select a Zapiet or Bird Widget
• After adding products and addresses, shoppers will be shown available local and shipping options. We pull the available dates and times from the respective app.
• When generating orders, we add the delivery app's required data to the order so that a delivery is scheduled

This initial support requires some back-end set-up, so message us in the app when you're ready to explore or get started.