refactor(user): 역할/팀 변경 도메인 메서드 추가

Author: CSE-Shaco

src/main/java/inha/gdgoc/domain/user/entity/User.java

@@ -131,4 +131,6 @@ public void updatePassword(String password) throws NoSuchAlgorithmException, Inv
     public boolean isGuest() {
         return this.userRole == UserRole.GUEST;
     }
+    public void changeRole(UserRole role) { this.userRole = role; }
+    public void changeTeam(TeamType team) { this.team = team; }
 }