feat: replace CustomRuntimeException with SecurityException for existing Mosu users in OAuthUserService

Author: polyglot-k

src/main/java/life/mosu/mosuserver/application/oauth/OAuthUserService.java

@@ -5,8 +5,6 @@
 import java.util.Map;
 import life.mosu.mosuserver.domain.profile.repository.ProfileJpaRepository;
 import life.mosu.mosuserver.domain.user.entity.UserJpaEntity;
-import life.mosu.mosuserver.global.exception.CustomRuntimeException;
-import life.mosu.mosuserver.global.exception.ErrorCode;
 import lombok.RequiredArgsConstructor;
 import lombok.extern.slf4j.Slf4j;
 import org.springframework.core.ParameterizedTypeReference;
@@ -62,7 +60,7 @@ public OAuth2User loadUser(final OAuth2UserRequest userRequest)
         final UserJpaEntity oAuthUser = oAuthUserPersistenceProcessor.process(userInfo);
         if (oAuthUser.isMosuUser()) {
             log.info("모수 회원으로 가입된 사용자입니다: {}", oAuthUser.getLoginId());
-            throw new CustomRuntimeException(ErrorCode.ALREADY_MOSU_USER);
+            throw new SecurityException();
         }
         Boolean isProfileRegistered = profileRepository.existsByUserId(oAuthUser.getId());