[18.0][FIX] sale_exception: portal signature hangs on exceptions

[gal-adhoc]

Depends on OCA/server-tools#3741. Follow-up of #4255.

Problem

Signing a quotation in the customer portal hangs when an exception rule applies:

1. portal_quote_accept writes the signature and flushes: the order row is locked by the ongoing transaction.
2. _validate_order() → action_confirm() → detect_exceptions() writes the exceptions through a second cursor on that same row, and waits forever.

Even without the lock, the BaseExceptionError would roll back the signature, and its client handler only lives in web.assets_backend: the portal would show the raw {"src_model": "sale.order", ...} payload. The free order flow of website_sale goes through _validate_order() too.

Change

_validate_order() detects the exceptions without rollback (base_exception_no_rollback, scoped to these orders):

• Blocked orders stay unconfirmed, keep the signature and get an internal note listing the exceptions, so the salesperson sees why.
• The other orders are confirmed as before.

The customer still gets the standard "signed" message: this is the behavior before #4255, when the confirmation silently returned the popup action.

Open question

sale_loyalty also overrides _validate_order() and there is no dependency between both modules. If it ends up above sale_exception, it may try to invoice a zero-amount rewarded order that was not confirmed (with sale.automatic_invoice). Not handled here; feedback welcome.

Tests

tests/test_validate_order.py: blocked order (not confirmed, signature kept, note posted), order without exceptions (confirmed) and a mixed batch. The lock itself cannot be reproduced in a TransactionCase (a separate connection does not see the uncommitted order), so it was checked manually on a real server: the portal request answers in ~2s instead of hanging.

[UsmanGhias]

Clean patch for OCA/sale-workflow.

Observations:

• The targeted patch addresses the issue cleanly without introducing side effects across related models.

Ready for testing on standard environments.

Best,
Usman