[FEATURE]: add overtime (unpaid leave) absence type

[c0rydoras]

Is your feature request related to a problem? Please describe.

Describe the solution you'd like

An absence type that fills up the whole day but is 0h instead of employment.worktime_per_day

Describe alternatives you've considered

No response

Additional context

No response

Required

• I have checked past issues to see if this feature has already been requested.

[tongpu]

If this is going to be implemented it might require some additional logic in the worktime balance mail being sent to supervisors each week to highlight that an employee might have worked less, but that it was to reduce their overtime.