anchor.diff:  
   User Groups are returned as an array under *user_groups*.
   
  -+ Model (application/vnd.api+json)
  -
  -    + Body
  - 
  ++ Model
  +
  +    + Body
  +
               {
                    "links": {
                       "user_groups.projects": {
  
positive.code: Creating a Project Role resource requires a link to a user and a
  project. You may also include an array of roles.
  
  + Request (application/vnd.api+json)
  
          {
              "project_roles": {
                  "roles": ["collaborator"],
                  "links": {
                      "project": "1",
                      "user": "842"
                  }
              }
          }
  
  + Response 201
  
  
negative.code: 
  ProjectRoles are returned as an array under *project_roles*.
  
  + Model
  
      + Body
  
  