protected LoggingDecoratorBuilder defaultLogger(Logger defaultLogger) {
        requireNonNull(defaultLogger, "defaultLogger");
        this.defaultLogger = defaultLogger;
        return this;
    }
Sets the logger that is used when neither {@link #logWriter(LogWriter)} nor {@link #logger(Logger)}
is set.
core/src/main/java/com/linecorp/armeria/common/logging/LoggingDecoratorBuilder.java