Italian Localization - Causali pagamento

This module adds a small reference table for Italian payment reason codes ("causali di pagamento"), the codes used, for example, on withholding tax (ritenuta d'acconto) documents.

Where it appears: - A new menu "Causali pagamento" under the Italian localization menu in Accounting. - A list and a form screen showing two fields: a short Code (maximum 2 characters) and a Description.

What users can do: - All internal users can read the list of codes. - Only Accounting managers can create, modify or delete codes.

Business rules and automatic behaviour: - Both Code and Description are mandatory. - The Code must be unique: if a user tries to save a code that already exists, Odoo blocks the save and shows an error message. - When a code is displayed elsewhere in Odoo, it is shown as "code - description", shortened to 50 characters if the description is long.

The module comes with a ready-made list of official Italian codes (A, B, C, ... ZO, L1, M1, M2, O1, V1) with their full descriptions, so users do not have to type them in. These pre-loaded records are marked as not updatable, so they are not overwritten by later module updates.

The module only touches its own causale.pagamento model and does not change invoices, taxes or other accounting documents.