reactivemongo.api.commands.AggregationFramework
The field name to become the new root
(Since version 0.20.3) No longer a case class
(Since version 0.20.3) No longer a case class
Promotes a specified document to the top level and replaces all other fields. The operation replaces all existing fields in the input document, including the _id field. https://docs.mongodb.com/manual/reference/operator/aggregation/replaceRoot