Takes the value from the header named after the constant SyncTokenHeaderName
and adds it to our list of accumulated sync tokens.
If given an empty value (or undefined) it clears the current list of sync tokens.
(indicates the service has properly absorbed values into the cluster).
Sync token tracker (allows for real-time consistency, even in the face of caching and load balancing within App Configuration).
(protocol and format described here) https://github.com/Azure/AppConfiguration/blob/master/docs/REST/consistency.md