Bug introduced by: https://github.com/odoo/odoo/commit/25d0c760bbfabb3cc7d471b08b5b06fe1cfc2ec4

**Steps to reproduce the bug:**
- Install the “Sales” module.
- Do not enable the "Units of Measure" option in the settings.
- Create a new quotation.
- In the sale order line, enable the Product Variant field.
- Try to create a new “product.product”

**Problem:**
A validation Error is triggered:

```
The operation cannot be completed
 - Create/update: a mandatory field is not set.
- Delete: another model requires the record being deleted. If possible, archive it instead.

Model: Product (product.template) Field: Unit of Measure (uom_id)

```
**Explanation:**
This happens because a default value for the UoM is passed through the
context. As a result, we skip the computation of “uom_id”:
https://github.com/odoo/odoo/blob/2b38c1f446441e04f8d85125a9ec6562d13b7ce8/addons/product/models/product_template.py#L27

However, this default is derived from the field “product_uom” that is
present in the view but restricted to users in the "uom.group_uom"
group. If the current user doesn't belong to this group (if you don't
enable the param in the settings), the field is hidden and its value is
empty, causing the default to be set to False.

https://github.com/odoo/odoo/blob/25d0c760bbfabb3cc7d471b08b5b06fe1cfc2ec4/addons/sale/views/sale_order_views.xml#L537


**Solution:**
Force the computation of “uom_id” by removing “default_uom_id” from the
context when its value is “False”.

opw-4717913

## Issue

When an employee has a flexible (unset) working calendar, and another employee has the default calendar (`Standard 40 hours/week`), scheduling a meeting involving both results in a `KeyError`:

```python
  File "/home/odoo/src/odoo/18.0/addons/hr_calendar/models/res_partner.py", line 78, in _get_schedule
    calendar_interval = interval_by_calendar[calendar][employee.resource_id.id]
                        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^
KeyError: <number>
```

## Root Cause

Odoo uses the Standard 40 hours/week calendar (resource.resource_calendar_std) as a fallback for flexible (unset) calendars. However, when grouping resources by their calendars, resources without a calendar are included in a separate group. 
Later, when Odoo computes work intervals per calendar, it assigns the default calendar to resource.resource(). If another user already uses the same calendar, the group duplication results in one being overwritten during iteration—causing the KeyError.

## Fix
Before grouping resources by calendar, explicitly assign the default calendar (resource.resource_calendar_std) to any resource that lacks a calendar. This ensures all resources are grouped correctly, avoiding duplication and key errors.

## Impacted versions:
18.0 and later

## Steps to Reproduce
### Pre-requisites:

- Install `hr_contract`, `calendar` apps.

### Steps:
1. Create **Employee 1**:
    - Set **Working hours** to **Flexible** (unset)
    - Create a **Contract**:
        - Set **Working hours** to **Flexible** (unset)

2. Create **Employee 2**:
    - Set **Working hours** to **Standard 40 hours/week**
    - Create a **Contract**:
        - Set **Working hours** to **Standard 40 hours/week**
        - Ensure the XML ID is `resource.resource_calendar_std`

3. Open the **Calendar** app.
4. Create a **new Event**.
5. Add both employees as **attendees**.

## Current Behavior  
The system raises a `KeyError` and does not allow the event to be saved.

## Expected Behavior
The event is saved successfully with both attendees.

### Task
OPW-[4699028](https://www.odoo.com/odoo/my-tasks/4699028)

---
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The original script is slow on large tables (more than 100000 records) because
of multiple sql queries. We reworked it so it's now one query exploded on chunks
which speeds it up a lot.

|                  | **Chunk size** | **Table**      | **Records** | **Total time (hh:mm:ss.)** | **Time/1000 records** |
|------------------|----------------|----------------|-------------|----------------------------|-----------------------|
| Multiple Queries | 100000         | pos_order      | 354881      | 0:41:47.438305             | 0:00:06.269000        |
| Multiple Queries | 2000           | pos_order      | 354881      | 0:02:11.708014             | 0:00:00.371000        |
| Single Query     | 100000         | pos_order      | 354881      | 0:00:14.724486             | 0:00:00.041000        |
| Exploded Query   | 100000         | pos_order      | 354881      | 0:00:07.937863             | 0:00:00.022367        |
| Multiple Queries | 2000           | pos_order_line | 819189      | 0:07:39.805373             | 0:00:00.561000        |
| Single Query     | 100000         | pos_order_line | 819189      | 0:00:29.666529             | 0:00:00.036000        |
| Exploded Query   | 100000         | pos_order_line | 819189      | 0:00:12.124260             | 0:00:00.014800        |
| Multiple Queries | 2000           | pos_payment    | 365725      | 0:01:52.806145             | 0:00:00.308000        |
| Single Query     | 100000         | pos_payment    | 365725      | 0:00:10.894065             | 0:00:00.030000        |
| Exploded Query   | 100000         | pos_payment    | 365725      | 0:00:04.670350             | 0:00:00.012770        |

Description of the issue/feature this PR addresses:

Current behavior before PR:

Desired behavior after PR is merged:




---
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**Steps to reproduce:**
- Install Accounting

- Activate a foreign currency (e.g. EUR)
- Make sure there are several rates with today rate different than others
- Go to "Accounting / Configuration / Accounting / Chart of Accounts"
- Add a default tax to "Expenses" account

- Create an invoice:
  * Customer: [any]
  * Currency: [EUR] (i.e. the foreign currency)
  * Invoice Date: [a date in the past where the currency rate is different than today]
  * Invoice Lines: [any]
- Confirm the invoice

- Go to "Accounting / Reporting / Management / Unrealized Currency Gains/Losses"
- Set date filter to "Today"
- If there is no adjustement to do, check if the following message is displayed:
"You are using custom exchange rates. => Reset to Odoo’s Rate"
If it's the case, reset to Odoo's rate (i.e. Today's rate)
- Click on "Adjustement Entry" button:
  * Journal: Miscellaneous Operations
  * Expense Account: Expenses
  * Income Account: [any]
- Create Entry

**Issue:**
The values (debit/credit) of the created entry are 0, which is not the case when there is no default tax on the expense account.

**Cause:**
"_sync_dynamic_lines" is executed on the created entry. If a default tax is set on the expense account, "_sync_tax_lines" is also executed.
As only debit and credit values are set on the invoice lines of the entry (neither balance nor amount_currency), the sync method messes up with the value of debit and credit, resetting them to 0 (via multiple recompute).

**Solution:**
Skip invoice sync.
The values computed in "Multicurrency Revaluation Wizard" should be the ones that are used.

opw-4664255