static ResponseLogLevelMapper of(HttpStatusClass statusClass, LogLevel logLevel) {
        requireNonNull(statusClass, "statusClass");
        requireNonNull(logLevel, "logLevel");
        return log -> log.responseStatus().codeClass() == statusClass ? logLevel : null;
    }
Creates a new {@link ResponseLogLevelMapper} which returns the specified {@link LogLevel} if the given
{@link RequestLog#responseStatus()} belongs to the specified {@link HttpStatusClass}.
core/src/main/java/com/linecorp/armeria/common/logging/ResponseLogLevelMapper.java