Adding addCourse method in Administration class

src/main/java/org/example/Administration.java

@@ -26,6 +26,10 @@ public class Administration {
 
     }
 
+    public void addCourse(Course course){
+        courses.add(course);
+    }
+
     /**
      *
      * @param professorID the id of the professor you want to be deleted from the system