PayPal Integration Master PayPal payment integration including Express Checkout, IPN handling, recurring billing, and refund workflows. When to Use This Skill - Integrating PayPal as a payment option - Implementing express checkout flows - Setting up recurring billing with PayPal - Processing refunds and payment disputes - Handling PayPal webhooks (IPN) - Supporting international payments - Implementing PayPal subscriptions Core Concepts 1. Payment Products PayPal Checkout - One-time payments - Express checkout experience - Guest and PayPal account payments PayPal Subscriptions - Recurring bi…