{"due_date": "Invoice due date", "amount_due": "Outstanding amount", "company_name": "Your company name", "opt_out_link": "Unsubscribe URL", "payment_link": "URL to payment page", "company_email": "Your email", "company_phone": "Your phone number", "customer_name": "Customer full name", "invoice_number": "Invoice identifier", "currency_symbol": "Currency symbol", "tracking_pixel_url": "Open tracking pixel"}