Switzerland - ISR inpayment slip (PVR/BVR/ESR)

This module adds the ability to generate and print Swiss ISR payment slips from invoices. Once an invoice is confirmed, you can click a button to print the ISR report, which produces a PDF with one slip per page. The slip includes a scannable reference line, amount, bank details, and addresses, all formatted according to Swiss standards.

Key features: - On customer invoices, a new 'ISR ref' field shows the generated reference, and a 'Print ISR' button becomes available after validation. - The system automatically creates a payment slip record for each receivable move line when the invoice is validated, provided the invoice has a partner bank account with an ISR subscription number. - The ISR reference is computed using the bank's ISR-B customer ID, the partner number, and the invoice number, with a check digit. It is stored on the move line and propagated to analytic lines. - A batch printing wizard allows printing slips for multiple invoices at once, with error checking. - Configuration options are available in Accounting settings: you can adjust the position of the scan line, address, amount, and other elements on the slip, choose whether to include a background image, and set the merge mode for batch printing. - On bank accounts, you can specify an ISR-B internal ID and choose whether to print the bank name, account number, and partner address on the slip.

The module adds a new model l10n_ch.payment_slip to store slip data, and extends invoices, move lines, bank accounts, companies, and settings. It also provides a report template for the ISR invoice report.