实现管理员对用户/课程的CRUD接口：
课程：
暂无
用户：
管理员：
server/src/main/java/com/example/controller/admin/AdminController.java
server/src/main/java/com/example/service/admin/AdminService.java
server/src/main/java/com/example/mapper/AdminMapper.java
server/src/main/resources/mapper/AdminMapper.xml
学生：
server/src/main/java/com/example/controller/admin/StudentController.java
server/src/main/java/com/example/service/admin/AdminService.java
server/src/main/java/com/example/mapper/StudentMapper.java
server/src/main/resources/mapper/StudentMapper.xml
教师：
server/src/main/java/com/example/service/admin/AdminService.java
server/src/main/java/com/example/mapper/TeacherMapper.java
server/src/main/resources/mapper/TeacherMapper.xml