Account Payment Mandate Sale

This module links direct debit mandates to sales orders. On a sale order, a new field "Direct Debit Mandate" appears next to the preferred payment method line, but only when the selected payment method requires a mandate.

• The mandate is automatically suggested from the invoicing contact's valid mandate for the same company. Users can still change it manually.
• The field is only shown when the payment method's configuration says a mandate is required.
• When the sale order is turned into an invoice, the chosen mandate is carried over to the invoice.
• The mandate list is filtered to show only mandates belonging to the invoicing commercial entity, in draft, valid or final state, and for the same company.

The module also adds a stored related field "Invoicing Commercial Entity" on the sale order, used to filter the available mandates. It touches the sale.order model and the sale order form view. No new menus or reports are added.