Context

Describe the background behind the problem.

Definition of done

• Move the "operation.Aggregate" type into the "mongo" package and unexport it.
  • Ideally keeping each operation type in its own Go file.
• Remove all exported setter methods.
• Update all code to use the moved "mongo.aggregate" type.
• Delete "x/mongo/driver/operation/aggregate.go"

Pitfalls

What should the implementer watch out for? What are the risks?