anchor.diff:  
   ## Data Structures
   
  -<!--### Choice (object)-->
  -<!--    + choice (string) - Text-->
  -<!--    + url (string) - Choice URL-->
  -<!--    + votes (number) - Number of votes-->
  -
  -<!--### Question (object)-->
  -<!--      + question (string) - Text of the question-->
  -<!--      + published_at (string) - An ISO8601 date when the question was published.-->
  -<!--      + url (string, required) - URL -->
  -<!--      + choices (array[Choice]) - An array of Choice objects.-->
   
   # REST API
   
  
positive.code: 
          {
          "subscriptionId": "52a745e011f5816465943d59"
    }
  
  + Response 201 (application/json)
  
      + Headers
  
              Location: /ngsi9
  
      + Body
  
              {
  "statusCode": {
    "code": "200",
    "reasonPhrase": "OK"
  },
      "subscriptionId": "52a745e011f5816465943d59"
    }  
    
    
    
  
  
  
  
negative.code: + Request (application/json)
  
          {
          "entities": [
          {
           "type": "Room",
           "isPattern": "true",
           "id": ".*"
          }
          ],
          "attributes": [
          "temperature"
          ],
          "reference": "http://localhost:8080/accumulate",
          "duration": "P1M"
          }
  
  + Response 201 (application/json)
  
      + Headers
  
              Location: /ngsi9
  
      + Body
  
              {
              "duration": "P1M",
              "subscriptionId": "52a745e011f5816465943d59"
              }
    
  ### Update Subscription to Context availability operation [POST /updateContextAvailabilitySubscription]
  
  