create holiday should select all child offices when parent office is selected (to make it hierarchical)

[bharathcgowda]

Description

while creating a holiday, office selection is a checker where a user has to select one office at a time, we have to make the office select hierarchical, for example, if we select head office by default all offices under head office should be selected.

Steps to Reproduce

1. create multiple offices under head office (this is for an example to demonstrate hierarchical structure)
2. go to admin->organization->manage holidays->create office
3. select head office( it should auto-select all the offices under head office) but the app only selects head office

Expected Behaviour

System should auto-select all the offices under the head office, (or any other parent office) In general, system should select all the child offices when a parent office is selected

Actual Behaviour

Screenshots, if any