[Feature]: Support for Braintree Drop In

[mdavo6]

How the project can be improved?

Currently out of the box payment support is limited to Stripe card element. Braintree is popular with merchants as it offers support for Paypal, and is supported in the Spree community via the spree_braintree_vzero gem. Adding OOB support for Braintree would give merchants greater flexibility in accepting payments.

What are the acceptance criteria?

• Generate Braintree token using call to new Braintree API endpoint.
• Initialize Braintree drop in UI using Braintree token.
• Submit payment details from the drop in UI to Braintree.
• Save payment details returned from Braintree to Spree.
• Complete order on successful payment.

Additional information

Note: Requires spree_braintree_vzero gem with new Braintree API endpoint and permitted attributes --> (PR to be added)

Code of Conduct

• I agree to follow this project's Code of Conduct