[ADD] supplier_portal: module for uploading vendor bills

[pamd-odoo]

This module allows portal users (vendors) to upload their bills through the website. A dedicated page with a form was added, containing:

• Organization name
• PDF file upload
• XML file upload Submitting the form creates a draft bill (account.move) in the backend, with the uploaded files attached to the bill as attachments.

[robodoo]