Payment methods - Absa Pay

Published documentation for the Absa Pay payment method in South Africa.

• Payment methods: Added Absa Pay to the South Africa section.
• Payments API release notes: Added the 2026-03-23 section.
• Checkout release notes: Added the 2026-03-23 section.
• Checkout webhooks: Added ABSAEFT to the relevant webhooks.
• Test and go live procedure: Added the Absa Pay section.
• Updated Payments API's API reference section with the virtualAccount array that merchants should use with the PEACHEFT paymentBrand to process Absa Pay transactions.
• Updated the Checkout (defaultPaymentMethod) API reference section with ABSAEFT.