[FIX] sale_project: sale_line_id shows SOs of child contacts

Current behaviour:
Sale Order Items on a task shows only SO related to the current
customer, or all SO if there is no customer on the task.

Expected behaviour:
If we have a customer on the task, show also SOs from child contact
of that customer (mirror the SO count in `Contacts` app)

Steps to reproduce:
- Install Contacts, Sales, Field Services
- Create 4 contacts, a company, with child contact A and B, a
  contact C who is child of A
- For each contact create an SO and confirm a field service product
- Now on any task, add the company as customer.
- In the Sale Order Item we can't select any of the SOs from the
  child contacts of the company.

Reason for the problem:
Since 41116c81cd where we wanted to
show all SOs when no `partner_id` was set on the task, we made use
of `=?` operator which is `True` when there is no `partner_id`, but
it matched only for `=` when it's not the case, not taking into
account `child_of` of said contact.

Fix:
Extend the domain with an `OR` to take child contacts if the
`partner_id` is not `False`.

Affected versions:
- 16.0
- saas-16.1
- saas-16.2
- saas-16.3
- master

opw-3374191

closes odoo/odoo#126898

X-original-commit: 027ba2e682ba046459fc60a76e59792fa6bbeda9
Related: odoo/enterprise#43395
Signed-off-by: Xavier Bol (xbo) <xbo@odoo.com>
Signed-off-by: Piryns Victor (pivi) <pivi@odoo.com>

addons/sale_project/models/project.py

@@ -700,7 +700,12 @@ class ProjectTask(models.Model):
         'sale.order.line', 'Sales Order Item',
         copy=True, tracking=True, index='btree_not_null', recursive=True,
         compute='_compute_sale_line', store=True, readonly=False,
-        domain="[('company_id', '=', company_id), ('is_service', '=', True), ('order_partner_id', '=?', partner_id), ('is_expense', '=', False), ('state', '=', 'sale')]",
+        domain="""[
+            ('company_id', '=', company_id),
+            '|', ('order_partner_id', 'child_of', partner_id if partner_id else []),
+                 ('order_partner_id', '=?', partner_id),
+            ('is_service', '=', True), ('is_expense', '=', False), ('state', '=', 'sale')
+        ]""",
         help="Sales Order Item to which the time spent on this task will be added in order to be invoiced to your customer.\n"
              "By default the sales order item set on the project will be selected. In the absence of one, the last prepaid sales order item that has time remaining will be used.\n"
              "Remove the sales order item in order to make this task non billable. You can also change or remove the sales order item of each timesheet entry individually.")