Slightly improve session refresh
Slightly improve session refresh

Previous solution of assuming that session is valid for at least N amount of seconds is pretty optimistic, too optimistic for real usage, instead, we won't assume anything like that and force every request to go through session refresh, but at the same time limit session refresh checks to just one at a time - if additional requests asked for session refresh, they'll use already-calculated value.

This way sending 100 requests at once won't always trigger 100 session refreshes but most likely around 2-3, while still allowing ASF to check session refresh with every request, if deemed necessary (due to delay between session checks

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