anchor.diff:  --------------------------------------------------
   PUT my_index/doc/3?routing=1&refresh <1>
   {
  -  "text": "This is a grand child document",
  +  "text": "This is a vote",
     "my_join_field": {
  -    "name": "grand_child",
  +    "name": "vote",
       "parent": "2" <2>
     }
   }
  
positive.code:                 "_score": null,
                  "_routing": "1",
                  "_source": {
                      "text": "This is a another child document",
                      "my_join_field": {
                          "name": "my_child",
                          "parent": "1"
                      }
                  },
  
negative.code: // CONSOLE
  
  <1> The name for the field
  <2> Defines a single relation where `question` is parent of `answer`.
  
  To index a document with a join, the name of the relation and the optional parent
  of the document must be provided in the `source`.
  For instance the following creates two parent documents in the `question` context:
  
  [source,js]
  --------------------------------------------------
  PUT my_index/doc/1?refresh
  {
    "text": "This is a question",
    "my_join_field": {
      "name": "question" <1>
    }
  }
  
  PUT my_index/doc/2?refresh
  {
    "text": "This is a another question",
    "my_join_field": {
      "name": "question"
    }
  }
  --------------------------------------------------
  // CONSOLE
  // TEST[continued]
  
  <1> This document is a `question` document.
  
  When indexing parent documents, you can choose to specify just the name of the relation
  as a shortcut instead of encapsulating it in the normal object notation:
  