This update fixes an issue where payslips weren't correctly generated for employees registered within branch companies of a larger organization. The fix adjusted the system's search criteria to include all related companies within the organizational hierarchy, ensuring accurate payslip creation. This improves payroll accuracy and reporting for businesses with multiple branches.

Bug: employees registered on branch companies don't appear in the
employee_id field when creating a payslip from the parent company.

Reason: the domain used ('company_id', '=', company_id) which only
matches the exact company, not its children.

Solution: replaced '=' with 'child_of' to include all descendant
companies in the hierarchy.

task - 6299634