feat: added validation for shiftAttendance

[ajablaza]

feat: Add attendance check-in/out validation to completeShift

Summary

Adds guard attendance validation to the completeShift route, preventing a shift from being marked complete unless the assigned guard has both checked in and checked out.

Changes

Shift Model (Shift.js)

• Added attendance virtual populate referencing ShiftAttendance via shiftId
• Added hasCheckedIn virtual — returns true if attendance.checkInTime is not null
• Added hasCheckedOut virtual — returns true if attendance.checkOutTime is not null

completeShift Route

• Returns 400 with 'Guard has not checked in' if hasCheckedIn is false
• Returns 400 with 'Guard has not checked out' if hasCheckedOut is false

Why

Previously, a shift could be completed without any attendance record, which could lead to inaccurate shift data. This validation ensures attendance is properly recorded before a shift is closed out.

Test Cases:
Unable to mark complete without guard checkin

Unable to mark complete without guard checkout

Shift completed after complete checkin/checkout from guard

[uppalkrish]

Good work!