Add client ID to Google Analytics requests

[davidfischer]

This almost reverts #4347 but is slightly different as it sends a client ID instead of a user ID.

Google's documentation says that the client ID should be a UUID but in my testing and in Google's own JavaScript implementation this works without that being the case.

[humitos]

I think that I can't really review this in a good way, but after the deploy you said that the data we wanted to see in analytics wasn't being shown properly.

I guess this should be fine for now.

We may want to add a comment here explaining that what the docs says doesn't work as it should be and also maybe create a ticket to track this in the future and change it if we find that google fixes it?.

[ericholscher]

Yea, it feels a bit like shooting in the dark here. Did we test this locally against GA, and see that it worked? That seems like the best way to figure it out without having to deploy it.

[davidfischer]

Did we test this locally against GA, and see that it worked?

Yes I did.

[davidfischer]

Just to clarify, when I removed the user ID, I did so based solely on the documentation which doesn't appear to be correct.

With adding this client ID, I tested an event with a client ID, saw it in the real-time report, and waited a day and saw it in processed reports.