During a previous fix (https://github.com/odoo/odoo/pull/206158), fallback values were added for an explicit `email_to` if the default email template for the abandonned cart was missing them.

But since (https://github.com/odoo/odoo/pull/172714), the template uses `use_default_to` == True, which will compute the default partner and add them to `partner_ids` of the `mail.mail` record.

So the old bug of "abandoned cart email is sent twice" reappered: the if condition fails to account for `use_default_to` being set, so the partner email is set explicitly on `email_to` AND referenced in `partner_ids`, which de-facto sends the email twice to the customer on the sales order.

## FIX:
We account for `use_default_to` in the if condition before adding the fallback.

How to reproduce:
1) Setup a database with demo data and website_sale 
2) Visit the shop as a visitor, add stuff to your cart 
3) Sign up for portal access and add new stuff to cart (will attribute SO to new portal account)
4) Wait for the abandoned cart email to trigger (can be forced by playing with `cart_recovery_email_sent`: false,`is_abandoned_cart`: true and triggering the CRON) -> mail is sent twice to the customer

Remarks:
- changed the unit test to actually capture the generated `mail.mail` and apply some asserts on it

OPW-6134731

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Forward-Port-Of: odoo/odoo#261039

Steps to reproduce:
- Ensure:
  - Marc Demo is a “Project” admin
  - All projects have “allow_task_dependencies” set to false. This will remove the “Use Task Dependencies” group from Role / User, so the order of these steps is important
  - Add Role / User implies “Use Task Dependencies”
- Sign in as Marc Demo and attempt to create a new project from the “Product Launch Campaign” template

Description:
`_inverse_allow_task_dependencies()` uses `_check_project_group_with_field()` to determine if task dependency features should be enabled/disabled by modifying the `hidden` field on `mail.message.subtype` records (e.g. `mt_task_waiting`). This occurs whenever a project is created from templates. However write access to these records are restricted to admins, so we need elevated permissions when attempting to do so. Without `sudo`, access errors are thrown if non-admin users attempt to create projects under specific scenarios (i.e. when `_check_project_group_with_field()` adds or removes a group from the user base group).

The search within `_check_project_group_with_field()` also needs elevated permissions to prevent false negatives. Without `sudo`, this search is restricted by the user's record rules. If the user cannot see the specific projects where dependencies are active, the system may incorrectly assume that no projects use these dependencies, and will forcefully unlink the dependency group from `base.group_user`, breaking the feature globally for all users.

Applying `.sudo()` to the subtype modification and the project search ensures standard users can create projects from templates without crashing and prevents the accidental global removal of the dependency group.

opw-6099425

Forward-Port-Of: odoo/odoo#258996

Previously, computing warning_employee_rate fetched all analytic lines associated with projects.task_ids to check if any employee lacked a sale_order_line in project.sale.line.employee.map.

This approach had two major flaws:

	1- Iterating over all accessible tasks is highly inefficient for
	large projects, especially since many tasks do not even have
	associated analytic lines.

	2- Fetching analytic lines blindly by task_id could pull in lines
	linked to a completely different project_id adding performance issues.

**Solution**:
Since the compute method for the `project_id` field for the `account.analytic.line` model is making sure that the field `project_id` equal the project for the task, then we can remove the domain matching for the `task_id`.

We now can replace the `_read_group` with a simple SQL query, filtering out the unmapped projects directly.

The benchmark done below was on a database that had around 10M analytic lines, 2K `project_sale_line_employee_map` records and 1M tasks with the top 80 projects in terms of the number of `analytic.lines` + projects that had the most records in the `project_sale_line_employee_map`.
| Before | After |
| :--- | :--- |
| 33.0s | 170.0ms |

Forward-Port-Of: odoo/odoo#260935

Steps to Reproduce
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- Assign a flexible working schedule to an employee (no leaves)
- Open Project > Tasks > Gantt view grouped by Assignee
- The employee's weekends and off-hours are grayed out

Current Behavior
---
Flex employees with no approved leaves in the viewed date range have incorrect grayed-out days in the Project Gantt view.

Expected Behavior
---
Flex employees should have no grayed-out days except approved leaves and public holidays.

Issue
---
When a flex employee has no leaves in the viewed period, `_get_unavailable_intervals()` returns an empty dict for that resource. `_gantt_unavailability()` then falls back to `company_leaves`, producing incorrect gray intervals. The same case is already handled in `planning` (ref PR), but `project_enterprise` was not covered.

Fix
---
Add a guard in `_gantt_unavailability()` to return no unavailabilities for flexible resources absent from `leaves_mapping`.

Related : https://github.com/odoo/odoo/commit/5f1cd39944134ffa2c30c331f8a5daca56446d78 
task - 5063071

Forward-Port-Of: odoo/enterprise#113247