fix: 카톡 bulk send 처리시 utf-8 추가

mens-core/src/main/java/kr/xit/core/spring/util/ApiWebClientUtil.java

@@ -127,7 +127,7 @@ public class ApiWebClientUtil {
     public <T> T exchangeKkotalk(final String url, final HttpMethod method, final Object body, final Class<T> rtnClzz, final CmmEnsRlaybsnmDTO ensDTO) {
 
         Map<String, String> map = new HashMap<>();
-        map.put(HttpHeaders.CONTENT_TYPE, MediaType.APPLICATION_JSON_VALUE);
+        map.put(HttpHeaders.CONTENT_TYPE, MediaType.APPLICATION_JSON_VALUE + ";charset=UTF-8");
         map.put(HttpHeaders.AUTHORIZATION, String.format("KakaoAK %s", ensDTO.getKakaoDealerRestApiKey()));
         map.put(Constants.JwtToken.PARTNER_REST_API_KEY.getCode(), String.format("KakaoAK %s", ensDTO.getKakaoPartnerRestApiKey()));
         map.put(Constants.JwtToken.SETTLE_ID.getCode(), ensDTO.getKakaoSettleId());