Update for Embedded Checkout

[NorthDevelopers]

The backend application has been migrated from using the legacy Browser Post API to North's Embedded Checkout API, refactoring the server to use ES modules. The update completely rewrites server.js, replacing the legacy TAC endpoints with secure /api/session and /api/complete endpoints to generate checkout sessions and verify transactions.

Technical Impact & Risks:

• New Environment Variables:
  • PRIVATE_API_KEY (Used for North's session generation)
  • CHECKOUT_ID (Identifies the checkout system)
  • PROFILE_ID (Identifies the merchant profile)
  • PORT (Configures the listening port, defaults to 8000)
• New Packages/Dependencies:
  • None
• Security Risks:
  • None detected (API credentials are securely loaded from environment variables; a .gitignore has been added to exclude .env).
• Testing:
  • No new tests detected
• Breaking Risks:
  • Legacy Browser Post API endpoints (/getTAC, /paymentResult, /getPaymentResult) have been completely removed, breaking compatibility with any un-migrated client applications.