part-time work Korea d-10 visa korea hikorea d10 student visa korea attendance rules student work permit Korea international student visa korea problems international student visa rejection Korea student visa korea rules international student korea immigration attendance korea job seeking visa korea D-2 visa Korea international student Korea student part time work korea visa study in Korea D-2 part-time job international student immigration review Korea student visa pattern issues Korea student visa attendance rules Korea international student administrative risk Korea student visa document mistake Korea Korean university visa student visa transfer Korea international student attendance Korea university change immigration Korea student visa after graduation international student job rules korea student visa instability Korea student visa korea attendance work rules international student korea immigration D-4 work permission student attendance Korea student visa Korea part-time work Korea international students