Summary

A user submitted a suggestion that we add an `addFields` method to our set of aggregation pipeline helper methods. (See PR here)

Motivation

This feature would allow `addFields` to be used builder style with the aggregation cursor, simplifying the syntax needed to use this stage otherwise.

How likely is it that this problem or use case will occur?

We don't know how often the `addFields` use case comes up relative to the other stages.