🐛 CORS 오류 수정

- 서비스 코드를 수정하였습니다.

src/main/java/com/committers/snowflowerthon/committersserver/auth/config/AuthenticationUtils.java

@@ -46,6 +46,14 @@ private static Authentication getAuthentication() {
     }
 
     private static CustomAuthenticationToken getCustomAuthenticationToken(Authentication authentication) {
-        return (CustomAuthenticationToken) authentication.getPrincipal();
+//        return (CustomAuthenticationToken) authentication.getPrincipal();
+        Object principal = authentication.getPrincipal();
+
+        if (principal instanceof CustomAuthenticationToken) {
+            return (CustomAuthenticationToken) principal;
+        } else {
+            // 처리할 로직이나 예외를 처리하는 코드를 추가할 수 있습니다.
+            throw new IllegalStateException("Unexpected principal type: " + principal.getClass());
+        }
     }
 }