Release adding Customer update support, expanded filtering, flexible order metadata date formats across payment flows and support for recurring payments.

### Added   
- Customers - Update Customer - PATCH `/2026-04-01/customers/{id}`

### Changed   
- Customers - List Customers now supports filtering by `emailAddress` - GET `/2026-04-01/customers`
- Payments - Order metadata line item dates now accept both `date` and `datetime` formats - POST `/2026-04-01/payment-intent`
- Payment Links - Order metadata line item dates now accept both `date` and `datetime` formats - POST `/2026-04-01/payment-links`, PUT `/2026-04-01/payment-links/{linkId}`
- Checkout Session - Updated with latest request/response structure - POST `/2026-04-01/checkout-sessions`, GET `/2026-04-01/checkout-sessions/{id}`, POST `/2026-04-01/checkout-sessions/{id}/proceed`
- Checkout Session - Customer object added to `/2026-04-01/checkout-sessions` to support recurring payments
- Checkout Session - `lineItems` object to accept additional Airline data, POST `/2026-04-01/checkout-sessions/{id}/proceed`