I run Meta Ads (Conversion objective) that push prospects straight into a WhatsApp Business API chat, where the entire payment happens inside WhatsApp. I already trigger basic purchase events with a home-grown script, but attribution is still blurry and repeat buyers are not being distinguished. I need a clean, server-side implementation of Meta’s Conversions API that • captures every completed payment in the WhatsApp Business API flow, • sends a deduplicated Purchase event to Meta with all the required matching parameters (event_id, fbp/fbc, ad_id, etc.), and • flags whether the buyer has purchased from us before so I can separate first-time revenue from repeat revenue inside Ads Manager and offline reporting. You can build in the language you prefer—Node, Python, PHP are all fine—as long as the code is well-documented and deployable on a standard Linux server. Acceptance is simple: once your solution is live I expect to see green-status Purchase events in Events Manager that match up to the corresponding ads, with a custom field (or parameter) clearly differentiating new vs. returning customers. Provide the minimal setup instructions and sample cURL calls so my team can maintain it going forward.