I need a developer who knows ERPNext’s payment framework inside out and who has already handled Elavon’s APIs. The goal is to plug Elavon into our ERPNext instance so that every payment flow—standard sales, refunds, and subscription renewals—runs flawlessly and PCI-compliantly. Scope of work • Wire up Elavon’s credit-card API to ERPNext, using server-side tokenization as the primary security mechanism. • Support both one-off and recurring transactions; they matter equally to us. • Allow customers who are logged in to: add a new card, remove an existing card, and update card details—all without exposing raw card data, relying on the token returned by Elavon. • Enable a “Pay Selected Invoices” action so a customer can clear several open invoices with a single charge. • Build full refund capability from within ERPNext and have status updates push back to the ledger automatically. • Deliver end-to-end tests (unit + functional) so I can run `bench --site mysite test` and watch everything pass before we go live. Acceptance criteria 1. A customer can complete, in production mode, a purchase, a refund, and a recurring renewal from the ERPNext web portal without errors or manual intervention. 2. Card data never hits our server logs or database; only Elavon tokens are stored. 3. The “Pay Selected Invoices” feature shows combined totals correctly and posts a single payment entry in ERPNext. 4. All three card-management actions (add, remove, update) work from the customer account page. 5. Automated tests cover each scenario above and pass on the latest ERPNext stable release. Please reply with a fixed price, a realistic turnaround time—including your own testing window—and any past ERPNext payment work you can point me to. Code must be clean, documented.