In this task, I implemented a supplier portal feature where a portal user can
log in and upload invoice files (PDF and XML) to automatically generate
a draft vendor bill in Odoo.

The portal homepage was extended by inheriting the existing portal template
and adding a new card.

On clicking the card, the supplier is redirected to an upload form where:
- Supplier can select the related organization
- Need to upload a PDF file.
- Need to upload a XML file.

After clicking Submit button:
- The system validates the selected company and uploaded files.
- A draft vendor bill is created.
- Both PDF and XML file are attached to the draft bill.
- A success or error message is shown accordingly.

Validation checks and security checks are implemented to ensure:
- Only portal user can access the feature.
- Suppliers can only select companies assigned to them.
- Files are validated before bill is created.

Task-5929548