Send scroll_id inside a json rather that text

[nomoa]

It's likely to cause issues with elastic 5.3 as Content-Type handling becomes
more and more strict.

eg.:
curl -H"Content-Type: application/json" -XGET localhost:9200/_search/scroll?scroll=1m -d 'DXF...'
now fails with Failed to parse request body on 5.3.x.
Elastic 5.1 was lenient and accepted this body and content-type.
Since we default Content-Type to application/json this is likely cause issues
in Elastica as well.
Using an array instead of plain string should force the use of a JSON body which is coherent
with the content-type we set.

[bgaleotti]

elastic/elasticsearch-php@59b3c08 looks the same

[ruflin]

@nomoa LGTM. Could you add a changelog entry?

[nomoa]

@ruflin done

[ruflin]

@nomoa Merged. Thanks.

[etudor]

Had the same problem with: ruflin/elastica 5.2.1 and elasticsearch 5.4.0

{
  "error": {
    "root_cause": [
      {
        "type": "illegal_argument_exception",
        "reason": "Failed to parse request body"
      }
    ],
    "type": "illegal_argument_exception",
    "reason": "Failed to parse request body",
    "caused_by": {
      "type": "json_parse_exception",
      "reason": "Unrecognized token 'DXF1ZXJ5QW5kRmV0Y2gBAAAAAAAHGKoWY3h2eGxBcHZUUGlINHRDa21USy0xUQ': was expecting ('true', 'false' or 'null')\n at [Source: org.elasticsearch.transport.netty4.ByteBufStreamInput@6d20e23; line: 1, column: 64]"
    }
  },
  "status": 400
}

Updating ruflin/elastica to dev-master solved the problem.

[ruflin]

The 5.3 release went out yesterday which should include this bugfix.