Support Mongo 3.2 syntax for $unwind in aggregation [DATAMONGO-1391]

[spring-projects-issues]

Mark Paluch opened DATAMONGO-1391 and commented

MongoDB 3.2 introduces an enhanced syntax for $unwind:

{
  $unwind:
    {
      path: <field path>,
      includeArrayIndex: <string>,
      preserveNullAndEmptyArrays: <boolean>
    }
}

The currently supported syntax contains only the path

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Reference URL: https://docs.mongodb.org/manual/reference/operator/aggregation/unwind/

Referenced from: pull request #355