Similar to #851 , we are attempting to begin the PAAPI auction in parallel with header bidding. However, we [acting as TLS] dont know interestGroupBuyers of the component sellers, who haven't yet provided their perBuyerSignals, at the time of the auction start, and we'd like to include interestGroupBuyers as a promise. We do know the list of components we might expect to participate.

This https://github.com/WICG/turtledove/blob/main/FLEDGE.md#211-providing-signals-asynchronously suggests this field is not on the list. Should we just list every possible buyer we can think of?