anchor.diff:  |===============
   |Response code|Description
   |201|Indicates the group was found and the member has been added.
  -|404|Indicates the userId was not included in the request body.
  +|404|Indicates the user was not included in the request body.
   |404|Indicates the requested group was not found.
   |409|Indicates the requested user is already a member of the group.
   
  
positive.code: [source,json,linenums]
  ----
  {
     "userId":"kermit"
  }
  ----
  
  
negative.code: [source,json,linenums]
  ----
  {
    "user" : null,
    "group" : "sales",
    "type" : "candidate",
    "url" : "http://localhost:8081/activiti-rest/service/runtime/tasks/100/identitylinks/groups/sales/candidate"
  }
  