anchor.diff:  
   ### Create a new context provider registration [POST /v2/registrations]
   
  -Creates a new registration. This is typically used for associating context sources
  -to certain data.
  +Creates a new registration. This is typically used for binding context sources
  +as providers of certain data.
   The registration is represented by a JSON object as described at the beginning of this section.
   
   Response:
  
positive.code: 
  # Group Registrations
  
  A Context Registration allows to bind external context information sources so that they can be play the role of providers
  of certain subsets (entities, attributes) of the context information space, including those located at specific geographical areas.
  A compliant Context Information provider shall expose an NGSI10 (legacy) or an NGSIv2 interface, in particular:
  
  * Query by entity type(s), entity id(s), geoquery and attribute and/or metadata projection (`attrs` or `metadata` parameter). (See `GET /v2/entities`)
  * Update entity attributes (See `PATCH /v2/entities/<entityId>/attrs`)
  When the entities or attributes covered by an active registered provider are the subject of a query or update operation, and the registrations allow to forward requests, 
  implementations must forward a request to such registered context provider so that it can provide the requested data or update it.
  The forwarding algorithm and precise implementation details are work to be completed in next versions of this specification. (*TODO*)
  
  A context registration is represented by a JSON object with the following fields:
  
  
negative.code:   Also, for registrations experiencing problems with forwarding operations, the status is set to `failed`.
    As soon as the forwarding operations start working again, the status is changed back to `active`.
  + `expires` : Registration expiration date in ISO8601 format. Permanent registrations must omit this field.
  + `forwardingInformation`: Information related to the forwarding operations made against the provider.
  Automatically provided by the implementation. 
  
  The `provider` field contains the following subfields:
  + `http` : It is used to convey parameters for providers which deliver information through the HTTP protocol.
  (Only protocol supported nowadays).
  It must contain a subfield named `url` with the URL that serves as the endpoint that offers the providing interface.
  The endpooint must *not* include the protocol
  specific part (for instance `/v2/entities`). 
  + `legacy` : `true` if this provider only supports NGSIv1 protocol. `false` if this provider supports NGSIv2.
  Currently `true` by default. In the future, will be changed to `false`. 
  