Freezer Client document structure

Identifies a freezer client for the purpose of sending action

client_info document contains information relevant for client identification

  "client_id": string   actually a concatenation "tenant-id_hostname"
  "hostname": string
  "description": string

client_type document embeds the client_info and adds user_id

client_type :
  "client" : client_info document,
  "user_id": string,    # owner of the information (OS X-User-Id, keystone provided, added by api)