Feature request

Current Issue:
The extension currently uses Stripe API version 2022-11-15, which doesn't support no-cost orders. This causes 100% discount promotion codes to be rejected as "invalid" even when they are valid codes.

Requested Change:
Update the Stripe API version to 2023-08-16 or later to enable support for no-cost orders.

Technical Details:

• Current API version: 2022-11-15 (in functions/src/config.ts line 43)
• Required API version: 2023-08-16 or later
• Reference: https://docs.stripe.com/payments/checkout/no-cost-orders