#8719796 Domains: Allow Multi-Year Domain Registration

Summary

This PR allows users to register a domain for multiple years by rendering a dropdown on the Checkout page.
• Adding support for plans and terms up to 10 years (decennial)
• Adding support for differentiating products based on volume

PT: pau2Xa-4UB-p2

Testing Instructions

Prerequisites

1. Add define( 'USE_STORE_SANDBOX', true ); to wp-content/mu-plugins/0-sandbox.php to sandbox the store so you can checkout with a test credit card
2. Sandbox public-api.wordpress.com
3. Apply D116538-code by running arc patch D116538 on your sandbox
4. Checkout this branch
5. Run yarn and yarn start

Testing

1. Go to http://calypso.localhost:3000/start
2. Select a custom .com domain
3. Proceed to the Checkout page
4. For the Domain Registration product, confirm you see multiple options for the number of years the domain can be registered.
5. Open the Network tab and filter the transactions by me/shopping-cart
6. Click on the dropdown and choose a different option
7. Expand the Payload of the corresponding network request and verify the correct volume is being passed to the BE: volume: 1 for One Year,volume: 2 for Two Years and so on. Expand the Response and verify the correct volume is returned from the BE.
8. Verify the selection is reflected in the dropdown
9. Verify the selection is reflected in the dropdown on the Checkout page
10. Open the Network tab and filter the transactions by transactions
11. Use a test credit card to complete the purchase
12. Expand the Payload of the corresponding network request and verify the correct volume is being passed to the BE:
    volume: 1 for One Year,volume: 2 for Two Years and so on.

Testing Video