I want my customers to receive an automatic email when their invoice due date is getting close. The email should be generated without any manual intervention, triggered solely by the “due date approaching” rule I define in the system (for example, three days before the due date). Each message must include a PDF attachment that contains the full invoice details so the client can review the amount, line items, and reference numbers right from their inbox. Here is what I expect as a finished solution: • A background job or script that checks invoice dates on a schedule I can adjust. • An HTML-friendly email template that pulls the customer name, balance, and due date. • Automatic PDF generation populated with the exact invoice data already stored in my database. • The email sent out immediately once the trigger condition is met, with the PDF attached. If you prefer to work with common tools like SendGrid, Mailgun, AWS SES, or a framework-level mailer (Node, Python, PHP, Laravel, etc.) let me know; I am flexible as long as the flow remains fully automated. The code needs to be clean, well-commented, and easy for me to adjust later should I decide to add payment instructions or additional reminder stages.