Documents that are not connected to another business record are now handled consistently as unlinked, avoiding confusing grouping and display differences. Attachments remain visible in technical views for users with the right access, preserving existing visibility while improving clarity.

Purpose
=======
Use False instead of 'documents.document' when a document is not linked to a record.

Attachment still have 'documents.document' if not linked to a record, so users see
the attachment in the technical view if they have access to the document (otherwise
they won't see it).

Task-4532059

VoIP now uses shared translation helper logic from the broader web platform instead of keeping its own copy. This reduces duplication and helps keep phone-related interface text consistent and easier to maintain across Odoo.

Community counterpart: https://github.com/odoo/odoo/pull/211279

WhatsApp tests were updated to match a platform change in how messages are categorized. This helps keep WhatsApp-related behavior aligned with the main messaging system and reduces risk of future inconsistencies.

The community counterpart of this commit replaces "is_note", "is_discussion" and "subtype_description" fake message fields by "subtype_id" which exists on message. This commit adapts whatsapp tests after this change.

task-4676083

community: https://github.com/odoo/odoo/pull/209487