anchor.diff:  
   ## Conformance
   
  -All the interfaces described by this specification are mandatory and must be implemented in order to be compliant with. 
  +This specification describes the "full" compliance level.
  +
  +However, next iterations of this specification could define optionality
  +in some parts and the compliance level (or roles/profiles)
  +corresponding to them.
   
   # Specification
   
  
positive.code: Notifications must include a `Ngsiv2-AttrsFormat` header with the value of `attrsFormat` of the associated subscription,
  so notification receiver can know the format used without needing processing notification payload.
  
  ## Custom notifications
  
  NGSIv2 clients can customize HTTP notification messages using a simple template mechanism. The
  `notification.httpCustom` property of a subscription allows to specify the following fields subject
  
negative.code: Response:
  
  * Successful operation uses 204 No Content
  * Errors use a non-200 and (optionally) an error payload. See subsection on "Error Responses" for more details.
  
  + Parameters
      + entityId: Bcn_Welt (required, string) - Entity ID
  