Added failing tests for saving embedded records

Creating a new record and adding a new embedded record will result in two requests (embedded: 'always'):
- One POST request for the parent with the child record embedded
- One POST request for child record

The second request is not necessary, because the child is embedded in the first request.


Creating a new embedded record  on an existing parent results in a POST request to the childs url. My understanding is that it should perform a PUT request to the parents' url with the child embedded.