Hello, we're trying to figure out the best place to passback user/device specific data known server side at join and update time that we can use at generateBid() time for decisionning. Looking at the spec/API and various discussions it seemed that userBiddingSignals would be the best place however it's unclear if it's meant to be updated through updateURL. Going through trustedBiddingSignals could be an alternative but is less desirable than storing directly on device.

After testing it's clear that it doesn't get updated. I can confirm by looking at chromium code that this field is not covered by the update.

https://source.chromium.org/chromium/chromium/src/+/main:content/browser/interest_group/interest_group_storage.cc;l=1507
https://source.chromium.org/chromium/chromium/src/+/main:content/browser/interest_group/interest_group_storage.cc;drc=a056443eb4e1a5922ce82b2d11a7b4e64e01f5a6;l=1560

If this is intentional, should we update https://github.com/WICG/turtledove/blob/main/FLEDGE.md to reflect that?
Currently the document says:

The updateURL provides a mechanism for the group's owner to update the attributes of the interest group: any new values returned in this way overwrite the values previously stored (except that the name and owner cannot be changed, and prioritySignalsOverrides will be merged with the previous value, with null meaning a value should be removed from the interest group's old dictionary)

Thanks!