anchor.diff:  `ch.qos.logback.contrib:logback-jackson:0.1.5` and `com.fasterxml.jackson.core:jackson-databind`
   for this library to work.
   
  -In the end both libraries are similar, both are based on the Jackson library and produce one JSON document per line.
  +In the end these libraries are similar, both user the Jackson library to generate JSON.
  +Contrary to the above JSON examples which have been prettyfied to be human readable, producing one JSON document per line is better.
   This format is known as http://ndjson.org/[NDJSON] or and http://jsonlines.org/[JSON Lines].
   Logstash and Filebeat can easily read this kind of JSON file.
  
positive.code: 
  Having this kind of information allows to group logs by user, by request, by processing.
  Remember that logs may be scattered across different servers, on different time periods. 
  In short, these additional fields allow correlating logs belonging to the same scenario and finding answers to questions like "what was the user X doing when he met this nasty error?"
  
  Let's get back to the example, we saw the MDC stores extra information about logs.
  The MDC is usually based on a thread local variable, this has two drawbacks:
  
negative.code: == JSON logging with Logback
  
  At this point, a log is more than simple string, 
  it is qualified with useful information: timestamp, level, thread, user Id...
  How can we write this data structure on disk or send it over the wire to a log collection tool?
  We have to serialize it.
  For a human being, a simple text format as shown above is readable enough.
  However, for a machine, this is just a word soup without any structure.
  In short, to send structured logs to a log collection tool 
  and benefit from this structure (search by user, by thread...), 
  we must use a structured format, like JSON for example.
  
  Compared to the Syslog format, another popular log format, the JSON format
  
  * Can properly handle  multi-line logs like stack traces/call traces or messages containing line separators (wanted or not)
  * Is a versatile format and can have custom fields like user Id, transaction Id 
  