Lock Timesheet recall if system has closed timesheet

[#1]

We need a solution for locking timesheets once they have been closed by the system. Individual users should not have the ability to recall timesheets only admins in order to ensure no hours adjustments have been made once a time-period closes.

[#2]

I would go even further. I envision an additional status for timesheets like 'locked', which does not allow anyone but an administrator (or a finance function) to make a change to a timesheet.

This is something desperately needed for accurate revenue recognition of professional services.