Clarify access cut-off scenarios in case of attestation not available

[lbdvt]

The attestation is a single point of failure for running business using the Privacy Sandbox, and must be handled accordingly by Ad Tech participants.

The explainer says in 6. What happens if there are one-off errors in serving the attestation file? :

Access would be cut off only if the server checking the attestation file is repeatedly unable to validate it. A single error/serving issue would not cause access to be removed.

In order to adapt attestation serving and monitoring, could you please be more specific in the scenarios that would lead to API access removal? What's the expected SLA for attestation serving?

[dmdabbs]

The attestation is a single point of failure for running business using the Privacy Sandbox,...

Fetching sites' json and applying it on device.

Issue 1496838: Add UMA to record the attestation file version when corruption happens
We have seen many attestations file corruption from metric, for example, "PrivacySandbox.IsTopicsAllowedForContext". We would like to check the version of the file that leads to the corruption.

Issue 1464311: Add UMA metric for enrollment list parsing time, detection time and memory usage
Privacy Sandbox] Add UMA metric for time taken for attestations file becomes ready.
The goal of the metrics is to help us understand the gap between the use of Privacy Sandbox APIs and the time attestations map is ready. The attestations map is used to check whether the site that an API is concerned is attested or not.