We now use the driver native option for aggregate instead of a plain command execution. This is necessary as of MongoDB 3.6 the cursor option is required for aggregations changing the return and execution model.
Still we maintain the raw values of AggregationResult as we used to do before. However, relying on executeCommand to change aggregation behavior in custom code will no longer work.
Tested against MongoDB: 3.6.RC3, 3.4.9 and 3.2.6
Along the the way we opened up Aggregation itself to expose the AggregationOptions in use und deprecated the $pushAll option on Update since it has been removed in MongoDB 3.6.
Original pull request: #515.
4f78aacbf7