feat: toggle self leave approval for employees from HR settings

[asmitahase]

Issue

Immediately after employees create and save leave application they see the document with "submit" as primary action that can lead to confusion as to clicking submit is part of the leave application process. So the employees ended up submitting their own leaves even if a different leave approver was already set in the application.
Role permission do not help in case one employee is leave approver for another employee.

---

Before

self_leave_approval_before.mov

After

self_leave_approval_pwa_after.mov

Screen.Recording.2025-01-30.at.2.46.24.PM.mov

Fix

Added a new setting in HR Settings called Prevent self-approval for leaves even if user has permissions which is disabled by default to retain current behaviour.
The submit action is removed on leave application if the settings is checked. Setting is ignored if the leave application doctype has a workflow.
Added tests for when self approval is enabled/disabled
I'll update the documentation once this is merged, no-docs for now

[ruchamahabal]

Suggested change

	"label": "Enable Self-Approval For Leaves"
	"label": "Allow self approval for Leave Application"

Fieldname says allow so keep it consistent?

[ruchamahabal]

Based on this setting, Approval field should also become read-only - client-side change

[ruchamahabal]

Suggested change

	if (not self_leave_approval_allowed) and (
	self.employee == get_current_employee_info().get("name")
	if get_current_employee_info()
	else None and not get_workflow_name("Leave Application")
	):
	frappe.throw(_("Self-approval for leaves is not allowed"), frappe.ValidationError)
	employee_user = frappe.db.get_value("Employee", self.employee, "user_id")
	if (
	employee_user == frappe.session.user
	and not self_leave_approval_allowed
	and not get_workflow_name("Leave Application")
	):
	frappe.throw(_("Self approval for leaves is not allowed"))

• Simplify checks
• get_current_employee_info fetches additional columns that aren't required here. We only need to compare the session user.
• Drop frappe.ValidationError, that's the default exception
  

[ruchamahabal]

From the last internal discussion, leaving context here:

Approval field has perm level set by default so employees don’t have access to edit the field HR managers and leave approvers do
But when the user themselves are hr managers, you might want to prevent self-approving leaves for such users
So the need for the setting comes from prevention rather than allowance

"Prevent self approval even if the user has permissions" is a better way to communicate instead of allow

And for users who have all perms and self-approval is allowed (the above setting is disabled), we can directly show submit button and change status to "Approved" on submission. No need to click any extra buttons or play around with the fields