Data API aggregation $merge not working anymore

Good Day,

I’m attempting to run a $merge within an aggregation using the Data API. The solution that was provided on this thread is very high-level → Data API now fails with A pipeline with this stage must be run as a System User

Could someone please break this down and share the step by step process? There is no documentation that has been provided to assist with this.

Kind Regards

I have the same issue, any help would be appreciated. Also, the solution in linked thread feels more like a workaround. It’s been a couple of months since it was posted, maybe there is a better way to do this now?