anchor.diff:  
       {
           "unit" : "The time unit defining the group level of the time series",
  -        "category" : "The category used to count artifacts"
  +        "category" : "The category id used to count artifacts"
           "preferences" : {
               "colors" : [{
               "label" : "The category label that should be displayed with a particular color",
  
positive.code: Additional attributes when `type = 'table'`.
  
      {
          "columns" : "Category enumerating the columns",
          "rows" : "Category enumerating the rows"
      }
  
  * `columns`: a category `id` containing the values displayed in column titles. `Artifact` will be organized vertically according to the value of this category. This value is mandatory.
  
negative.code: 
  All messages related to the `User` data type are published to the `user` topic.
  
  ==== event = 'CREATE' OR event = 'READ' OR event = 'UPDATE'
  
  The `CREATE`, `READ` and `UPDATE` events for a `User` has a `data` attribute associated to a value that looks like this:
  
      {
          "email" : "The user email address", 
          "firstname" : "The user first name",
          "lastname" : "The user last name",
          "picture" : "The picture of user profile"
      }
  
  `READ` and `UPDATE` events are sent for a given `User` only to the consumers connected to an `Organization` that registers this `User` as a member.
  	
  *email*
  
  A string corresponding to the user email. Mandatory attribute.
  	
  *firstname*
  
  A string corresponding to the user first name. Optional attribute.
  
  *lastname*
  
  A string corresponding to the user last name. Optional attribute.
  	
  *picture*
  
  A `base64` string corresponding to the user picture. Optional attribute.
  
  ==== event = 'DELETE'
  
  The `DELETE` event for a `User` has a `data` attribute associated to an empty value.
  In fact, the event simply indicates that a `User` identified by the event `id` has been removed.
  Therefore, no more information than the `id` is required to identify the removed view.
  
  This event is sent for a given `User` only to the consumers connected to an `Organization` that registers this `User` as a member.
  
  === Organization
  
  All messages related to the `Organization` data type are published to the `organization` topic.
  
  ==== event = 'CREATE'
  
  The `CREATE` event for an `Organization` has a `data` attribute associated to a value that looks like this:
  
      {
          "name" : "The name of the organization",
          "picture" : "The picture of the organization",
          "members" : [{
                  "id" : "The ID of the organization member",
                  "role" : "The role of the member inside the organization"
          }]
      }
  
  This event is sent through this topic by producer when a new `Organization` is created.
  