This update corrects several point of sale issues involving refunds, taxes, discounts, and coupon rewards. It helps cashiers process refunds more accurately, prevents mistaken removal of active promotions, and ensures eligible products still receive the right promotional discounts.

Forward port of https://github.com/odoo/odoo/pull/75929


--
I confirm I have signed the CLA and read the PR guidelines at www.odoo.com/submit-pr

Point of sale invoices no longer add duplicate payment details because that information is now already included by the standard invoice layout. This keeps customer invoices clearer and avoids repeated payment references.

Forward port of https://github.com/odoo/odoo/pull/75844

--
I confirm I have signed the CLA and read the PR guidelines at www.odoo.com/submit-pr

This update fixes several Point of Sale issues around refunds, discounts, taxes, coupons, and invoice payment details. It helps cashiers process refunds more accurately, prevents accidental coupon removal, and avoids duplicate or incorrect payment information on invoices.

Forward port of:
* https://github.com/odoo/odoo/pull/75844
* https://github.com/odoo/odoo/pull/75929

--
I confirm I have signed the CLA and read the PR guidelines at www.odoo.com/submit-pr

This update corrects how electronic invoicing data is converted for transmission, preventing formatting errors caused by Base64 handling. It helps ensure Italian e-invoices and proxy registration data are prepared correctly and sent more reliably.

When encoding a string or bytes with base64, the resulting byte string must be decoded to get the string back.

* `addons/account_edi_proxy_client/models/account_edi_proxy_user.py`
  AccountEdiProxyUser._register_proxy_user()

* `addons/l10n_it_edi/models/account_invoice.py`
  AccountMove._prepare_fatturapa_export_values()

* `addons/l10n_it_edi_sdicoop/models/account_edi_format.py`
  AccountEdiFormat._l10n_it_post_invoices_step_1()