MPESA Gateway Integration for E-Commerce

I need someone who has already connected MPESA to a live shopping site and can do it again quickly and cleanly on my existing e-commerce store. The task is to wire the Safaricom MPESA APIs into the checkout flow, make sure payments are confirmed in real time, and have the order status update automatically once a transaction is successful or flagged when it is not.

You will be given:
• API credentials and test credentials from Safaricom
• Full access to the site’s codebase and hosting panel
• A staging domain for initial implementation

Key expectations:
• Build the integration with the current cart and checkout logic so customers never leave the site.
• Handle all required callbacks (STK Push, validation, confirmation, timeout).
• Record MPESA receipt codes against the order for later reconciliation.
• Provide clear, human-readable documentation of the steps taken for future maintenance.
• Run end-to-end tests on staging, then deploy to production with minimal downtime.

Please respond with a brief outline of how you plan to structure the integration, any libraries or SDKs you prefer, and a link to at least one live MPESA implementation you have delivered.