App Integrations: Payments, WhatsApp, Instagram

My app already runs smoothly on both iOS and Android, but the external services it relies on still need to be wired up. I want every major integration—payments, social, and messaging—implemented end-to-end so users enjoy a seamless experience without ever leaving the app.

Payment gateway
I have not locked myself into a single provider, so feel free to recommend the best fit (PayPal, Stripe, Square, or another PCI-compliant option). What matters most is secure tokenised transactions, flawless webhook handling for success / failure events, and clear error reporting in the UI.

Instagram
Users should be able to sign in with Instagram, pull basic profile data, and optionally share selected content from inside the app. Standard Instagram Graph API flow with refreshable long-lived tokens will do the job; just make sure rate-limit handling is in place.

WhatsApp
A tap on a product or support button should open a pre-filled chat through the official WhatsApp API / deep link so users can reach us instantly. If you know a better supported method, I’m open.

Deliverables (all source, fully tested)
• Payment gateway integration with test and live modes enabled
• Instagram authentication and share endpoints wired to existing screens
• WhatsApp chat launch, including dynamic message templating
• Clear setup documentation so a future dev can re-deploy or swap credentials in minutes
• Brief hand-off call or recorded walkthrough once everything is merged

Provide your timeline and any API-rate or store-review caveats you foresee, and I’ll supply the current codebase plus environment keys right away.