anchor.diff:  
   The editors would like to express their gratitude to the following people who actively
   contributed to this specification:
  -Juan José Hierro (Telefónica I+D), Marcos Reyes (Telefónica I+D), Ken Zangelin (APInf, formerly with Telefónica I+D),
  +Juan José Hierro (Telefónica I+D), Marcos Reyes (Telefónica I+D), Ken Zangelin (Telefónica I+D),
   Iván Arias León (Telefónica I+D), Carlos Romero Brox (Telefónica I+D),
   Antonio José López Navarro (Telefónica I+D),  Marc Capdevielle (Orange), Gilles Privat (Orange), 
   Sergio García Gómez (Telefónica I+D), Martin Bauer (NEC).
  
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`)
  
negative.code: + `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 endpoint must *not* include the protocol
  specific part (for instance `/v2/entities`). 
  + `supportedForwardingMode` : It is used to convey the forwarding mode supported by this context provider. By default `all`. 
  Allowed values are:
      + `none` : This provider does not support request forwarding.
  