public LogWriterBuilder successfulResponseLogLevel(LogLevel successfulResponseLogLevel) {
        requireNonNull(successfulResponseLogLevel, "successfulResponseLogLevel");
        return responseLogLevelMapper(log -> log.responseCause() == null ? successfulResponseLogLevel : null);
    }
Sets the {@link LogLevel} to use when logging successful responses (e.g., no unhandled exception).
{@link LogLevel#DEBUG} will be used by default.
core/src/main/java/com/linecorp/armeria/common/logging/LogWriterBuilder.java