I need a clean, production-ready BillDesk payment gateway added to the mobile app that sits on my Odoo 18 back-end. The goal is simple: let users pay directly from the app and have each transaction flow back into Odoo so orders and invoices move automatically into their paid state. The work involves: • Creating an Odoo module that handles token generation, checksum/secure hash requirements, and the BillDesk redirect → callback cycle • Building the mobile-side hand-off so the user sees the BillDesk screen in-app, completes payment, and is returned seamlessly with success/failure messaging • Updating Odoo sales orders, invoices, and accounting entries the moment BillDesk confirms a payment • Supplying clear setup notes and a quick test script so my team can replicate the flow on staging before we push to production Everything must be fully tested on the current Odoo 18 codebase. If extra hooks or controllers are required in the app layer, document them; otherwise the finished Odoo module should drop in with minimal code changes on the mobile side. Once you hand over the module, callback URLs, and documentation, I will run end-to-end tests to sign off.