public static void setUserMetadataHeaders(Map<String, String> userMetadataMap,
      RestResponseChannel restResponseChannel) {
    setUserMetadataHeaders(userMetadataMap, restResponseChannel, Collections.emptySet());
  }
Sets the user metadata in the headers of the response.
@param userMetadataMap map of user metadata that needs to be sent.
@param restResponseChannel the {@link RestResponseChannel} that is used for sending the response.
@throws RestServiceException if there are any problems setting the header.
ambry-api/src/main/java/com/github/ambry/rest/RestUtils.java