Automated GST E-Invoice Upload

My custom-built billing cart (PHP with a MySQL back end) already generates the IRN-ready JSON for every sale. What I still lack is an automated way to place that file on the Government GST e-invoice portal without the extra OTP step that normally interrupts the flow... (Budget: ₹600 - ₹1500 INR, Jobs: API Development, Automation, Database Management, Software Architecture, Web Development, XML)