feat: includes sections on external services in the README, with explanations and links to documentation, detailing how comanda processes payments and manages collections.

Author: https-richardy

README.md

@@ -56,3 +56,23 @@ Each directory represents an independent system with its own solution, source co
 | CI/CD | GitHub Actions | Autonomous pipelines per bounded context |
 
 </div>
+
+---
+
+<h4 align="center">EXTERNAL SERVICES BEHIND COMANDA</h4>
+
+#### PIX Transactions
+
+> Comanda integrates with **AbacatePay** to process PIX-based payments, enabling fast and localized transactions for Brazilian merchants.  
+This powers the real-time checkout experience used by stores when processing customer orders.
+
+- Website: https://www.abacatepay.com/
+- Documentation: https://docs.abacatepay.com/
+
+#### Subscription & Billing Infrastructure
+
+> As a SaaS platform, Comanda relies on **Stripe** to manage the full subscription lifecycle.  
+Recurring billing, subscription status, payment retries, and invoicing are orchestrated through Stripe’s infrastructure, ensuring platform monetization remains robust and operationally independent from merchant revenue flows.
+
+- Website: https://stripe.com/
+- Documentation: https://docs.stripe.com/