Proxy PvD: define failure mode for "expires" key #297
Description
PvD Additional Information is required to contain the "identifier", "expires", and "prefixes" keys.
The document defines the expires key but does not specify expected client behavior if the configuration expires and subsequent fetch attempts fail. Should the client continue using the last known configuration or revert to the initial configuration?
On one hand, the last configuration might have expanded the set of known proxies, on the other hand proxy-match section might become outdated and overly restrictive.