Message access is notably based on related document, given their
(model, res_id) pair. Model may customize the required access on
it in order to access their message. For example, you generally
need write access to create a message (post) but on some models
you can post when you can read. Calendar events message access depends
on calendar privacy settings.

This is controlled via '_get_mail_message_access'. However currently
it is "globally called", for all documents. It should be done on a
per-document basis, as each document could define different access
check.

Keep code somewhat optimized by doing access checks in batch for a
given operation.

Make _search and read symmetric. Reading documents should be allowed
on search results, and search results should match what is available
for reading.

Portal users have some specific domains applied when accessing
messages, see notably odoo/odoo@9cd9aaaa174ae1f2a0af12143a34eb4682ea6f59 (but also check for
'website_message_ids' domain, mail controllers, ...). However there
are still some cases where search and read are not coherent with
portal users. This is not really annoying as most messages are accessed
using sudo and correctly tailored domains via controllers but let
us try to have a more correct code.

Fix discuss display of chatter-related buttons
* not taking into account '_get_mail_message_access' to check if
  user has right to post (generally used to indicate users can
  post on readonly records, but not limited to that);
* not adding the same check on Activities button as on Send message
  and Log note. We consider generally that rights should be aligned
  and UX should match that behavior;
* not adding the same check on attachments buttons, currently limited
  to write access (or always accessible). This is a preliminary work
  for attachments, further fixes are probably incoming;

Mainly a backport of master improvement done at https://github.com/odoo/odoo/pull/214705 .

Task-5138368
opw-4785878

Forward-Port-Of: odoo/odoo#244009
Forward-Port-Of: odoo/odoo#233725

### Issue:
When a custom button snippet was dropped next to an existing button 
wrapped in a `<div>`, it was incorrectly and unconditionally wrapped in 
a paragraph `<p>` tag. This issue did not occur with standard button 
snippets or when the buttons were wrapped in a `<p>` tag.

### Steps to reproduce:
1. Drag a standard "Button" snippet next to an existing button (e.g., in
   the navbar). The structure is correctly `<a/><a/>`.
2. Save a button as a custom snippet.
3. Drag this new custom button snippet next to a button wrapped in a 
   `<div>` (navbar in our example).
4. Observe the structure: 
   `<div><a/><p><a class="s_custom_snippet"/></p></div>`,
   but it should be like `<div><a/><a class="s_custom_snippet"/></div>`.

### Fix
The logic has been corrected to only wrap a button snippet in a 
paragraph tag if it has no sibling buttons and is not already inside a 
`<p>`. This ensures consistent behaviour between standard and 
custom button snippets. A tour test is also added, ensuring the 
behaviour is correct.

Backport of https://github.com/odoo/odoo/commit/3a8f2cc418510c3b91f8b9086bb4a89a1745e40d

task-[5032130](https://www.odoo.com/odoo/project/974/tasks/5032130)

Forward-Port-Of: odoo/odoo#241937
Forward-Port-Of: odoo/odoo#224476

The base `_get_party_node` uses `commercial_partner.ref` for `PartyIdentification` and `commercial_partner.vat` for `CompanyID`. There was no logic to prefer `company_registry` when available.

Refs:
An independent invoice example: https://developer.vertexinc.com/einvoicing/docs/belgium-example-documents

https://github.com/odoo/odoo/blob/40c862476382c68d7f452284074f5b44955d1f98/addons/account_edi_ubl_cii/models/account_edi_xml_ubl_20.py#L1564-L1566

https://github.com/odoo/odoo/blob/40c862476382c68d7f452284074f5b44955d1f98/addons/account_edi_ubl_cii/models/account_edi_xml_ubl_20.py#L1585

Steps To Reproduce:
- Have accounting, account_edi_ubl_cii and contacts installed.
- Create a Belgian company and set the VAT, Company ID and Reference (under Sales & Purchase tab).
- Create a contact and set his eInvoice format in Accounting tab to EU Standard (Peppol Bis 3.0) and make sure to give him a country.
- Go to accounting -> Customers -> Invoices and create an invoice for the contact you created.
- Send the invoice to the contact and download the XML from the chatter and inspect it.
- PartyIdentification/ID shows the partner's ref field value (e.g., "(odoobe)") instead of the company registration number.
- PartyLegalEntity/CompanyID uses the VAT number instead of the company registration number (ondernemingsnummer).


Ticket [link](https://www.odoo.com/odoo/project.task/5418190)
opw-5418190

Forward-Port-Of: odoo/odoo#243143

In **l10n_ec**, negative lines are not accepted in the XML.
They must be dispatched as discounts on positive lines.
The dispatching logic implemented in `60e1b41734f76a2d9268edc41286462a9d01a501` can cause rounding issues when the decimal accuracy for `price_unit` is increased.

## Steps to reproduce

With **l10n_ec**:
1. Change the decimal accuracy to 6 digits.
2. Set the rounding method to *global rounding*.
3. Create an invoice with the following lines:

| Quantity | Price    | Taxes     |
|-----------|----------|-----------|
| 20        | 1.4235   | VAT 0% G  |
| 20        | 1.6425   | VAT 0% G  |
| 20        | 1.2337   | VAT 0% G  |
| 20        | 1.2337   | VAT 0% G  |
| 20        | 1.4235   | VAT 0% G  |
| 6         | 3.747768 | VAT 15% G |
| 6         | 3.747768 | VAT 15% G |


In the generated XML, some product lines show a `descuento` of `0.01` or `-0.01`.

This happens due to rounding differences in how the `descuento` is computed in the
`common_details_info_template` from **l10n_ec_edi**:

format_num_2(line_edi_values['price_discount'] + abs(line.balance) - line_items[1]['base_amount'])

where `line.balance` and `line_items[1]['base_amount']` can differ by 0.01 due to global rounding applied during tax aggregation, and that difference must be redistributed somewhere.

This commit changes how negative lines are dispatched onto positive ones, aligning the behavior with **l10n_mx**.
Instead of using `tax_details_per_record` to build the XML, we now use `base_lines`, where the negative lines have already been distributed.

opw-5128612