fix: missing user id in ga4 forwarder plugin

[liuyang1520]

Summary

fix: missing user id in ga4 forwarder plugin

Tested with a local setup:

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[Mercy811]

I think the problem is that the if condition is always false so that setUserId() is never called. Please see https://discourse.amplitude.com/t/ga4-events-forwarder-how-can-i-set-user-id-for-forwarded-event/15319/2.

[liuyang1520]

I think the problem is that the if condition is always false so that setUserId() is never called. Please see https://discourse.amplitude.com/t/ga4-events-forwarder-how-can-i-set-user-id-for-forwarded-event/15319/2.

@Mercy811 Thanks for reviewing! I think the event.user_id will always be undefined since it is deleted in previous line, my understanding is when we see a new userId, we setUserId and update the lastSeenGAUserId, so I don't think amplitude.setUserId(event.user_id) is correct. lastSeenGAUserId should be set during the iterations, when we see a new userId but no lastSeenGAUserId. Let me know if I miss anything, haven't touch the SDK code for a long time 😄

[Mercy811]

Thank you @liuyang1520