static LogFormatter ofJson(ObjectMapper objectMapper) {
        return new JsonLogFormatterBuilder()
                .objectMapper(objectMapper)
                .build();
    }
Returns a newly created {@link LogFormatter} that converts a {@link RequestOnlyLog} or
{@link RequestLog} into JSON format log message by using the specified {@link ObjectMapper}.
core/src/main/java/com/linecorp/armeria/common/logging/LogFormatter.java