User ID gets ignored #42
Description
Expectation
If you set User ID in the MC parameters, it should get sent, and be observable in GA4 BigQuery exports.
Observations
If you set User ID in the config, it gets sent with server side requests (as uid).
It's a little hard to tell if this works, because it doesn't show up in the DebugView in GA4. However, if you GA4 exporting to BigQuery, there's a user_id column for events. I found this was always null despite getting sent to GA4.
I have been troubleshooting by also firing requests client side with gtag, but was unable to figure out why the uid from the request wasn't showing up. The client side requests looks a bit similar, but is sent to another domain, and has many different parameters in addition to overlapping ones. Notably, the client side request with user_id set in the JavaScript, did map to a uid URL param also.
For the GA4 MC, I tried passing G111 for consent manually, setting custom params uid and user_id manually (not what we want since it sets event params).
For events sent client side, I was able to observe in BigQuery in seconds, which also confirms there's no config issue related to my tracker or property.
Potential solution
It seems like a lot of the current implementation is reverse engineered and depends unpublished API details to mimic a client side tag. However, there's a stable and published API for server side events. #17 (but for all events, except audiences), could solve this.