Task implementation course

See merge request !3

# Conflicts:
#   src/main/java/id/ac/ui/cs/advprog/tutorialo/controller/StudentController.java
#   src/main/java/id/ac/ui/cs/advprog/tutorialo/exception/DuplicateStudentNameException.java
#   src/main/java/id/ac/ui/cs/advprog/tutorialo/model/Student.java
#   src/main/java/id/ac/ui/cs/advprog/tutorialo/repository/StudentRepository.java
#   src/main/java/id/ac/ui/cs/advprog/tutorialo/service/StudentService.java
#   src/main/java/id/ac/ui/cs/advprog/tutorialo/service/StudentServiceImpl.java

Task implementation student

See merge request !1