Integrate AffiliateWP With Railway Emergency need in 24hrs or less

I already run AffiliateWP on my main WordPress install and want to keep it there, yet all sales now happen on a separate Railway-hosted site. Your job is to wire the two together so AffiliateWP continues to track referrals and calculate commissions even though the checkout takes place off-site. Here is the exact flow I need: • A shopper lands on the Railway site with an affiliate referral code (or pastes a code into a coupon / promo field). • At checkout that code is validated against AffiliateWP, the order is logged through the AffiliateWP REST API, and the correct commission is awarded. • If no valid code is present, the order proceeds without affiliate attribution. Key points • Only affiliate tracking and commissions are required—no user-account syncing or data warehousing. • The trigger is the use of an affiliate code, applied specifically at checkout on Railway. • Everything must stay compatible with core AffiliateWP features (status changes, manual adjustments, payout calculations). Deliverables 1. Lightweight integration module (Node/Express middleware, serverless function, or similar) that sends order data to AffiliateWP via its REST or PHP API. 2. Secure handling of the shared secret / OAuth creds. 3. Clear setup notes so I can redeploy if my Railway app is rebuilt. 4. A quick test plan proving that referred, non-referred, and invalid-code checkouts behave as expected. I am ready to supply API keys, staging URLs, and sample orders straight away, and I’ll respond quickly to questions so we can wrap this up efficiently.