New paid field on Supplier Invoices endpoints

The response of the supplier invoices endpoints now includes a paid boolean field. The field indicates whether the invoice is paid.

Impacted endpoints:

• List supplier invoices
• Retrieve a supplier invoice
• Import a supplier invoice with a file attached
• Update a supplier invoice
• Validate the accounting of a supplier invoice

This is a non-breaking change. The new field is additional and does not affect the existing response structures.