title: Modify @OneToMany entity in Spring Data Rest without its repository
body: <p>In my project I use object of type <em>A</em> which has OneToMany relation (orphanRemoval = true, cascade = CascadeType.ALL, fetch = FetchType.EAGER) to objects of type <em>B</em>. I need SpringDataRest (SDR) to store complete full <em>A</em> object with its <em>B</em> objects (children) using single one POST request. I tried several combinations in SDR, the only one which worked for me, was to create @RepositoryRestResource for object <em>A</em> and to create @RepositoryRestResource also for object <em>B</em>, but mark this (<em>B</em>) as exported=false (if I did not create repository out of object <em>B</em> at all, it would not work -> just <em>A</em> object would be stored on single POST request, but not its children (@OneToMany relation) of type <em>B</em>; the same outcome occurs if exported=false is omitted for <em>B</em> repository).
   Is this ok and the only way how to achieve it (single POST request with storing all objects at once)?</p>
  
  <p>The reason I'm asking, in my previous example, I have to (I would like to) control all objects "lifecycle" by using <em>A</em>'s repository. I am ok with it, because <em>A</em>-><em>B</em> relation is composition (<em>B</em> does not exists outside of <em>A</em>). But I have serious problem of editing (also removing) one certain object of type <em>B</em> by SDR using its parent repository (since object <em>B</em> doest not have its own repository exported). Maybe, this is not possible by definition. I have tried these solutions:</p>
  
  <ul>
  <li>PATCH for "/A/1/B/2" does not work -> method not allowed (in headers
  is "Allow: GET, DELETE") -> so, also PUT is out of question</li>
  <li>Json Patch would not work either - PATCH for "/A/1" using json patch
  content-type [{"op": "add", "path": "/B/2", ....}] -> "no such index
  in target array" - because Json Patch uses scalar "2" after "array"
  as a index to its array. This is not practical in Java world, when
  relations are kept in Set of objects - indexing has no meaning
  at all.</li>
  <li>I could export repository (exported=true) of object <em>B</em> for
  manipulating it "directly", but this way I would loose ability to
  store the whole object <em>A</em> with its <em>B</em> objects at one single POST
  request as I have mentioned before.</li>
  </ul>
  
  <p>I would like to avoid sending the whole <em>A</em> object with one single tiny   modification of its <em>B</em> object for PUT, if possible.
  Thank you.</p>