Optional TTL for caching positive (active:true) introspection results,
keyed by the raw token. Zero (the default) disables caching. Caching trades
revocation latency for performance: a token revoked at the AS, or one whose
own exp is sooner than the TTL, may be served as valid from cache until
the entry expires. Entry expiry is clamped to the token's exp (RFC 7662)
when present, so the staleness window never outlives the token itself.
Optional TTL for caching positive (active:true) introspection results, keyed by the raw token. Zero (the default) disables caching. Caching trades revocation latency for performance: a token revoked at the AS, or one whose own exp is sooner than the TTL, may be served as valid from cache until the entry expires. Entry expiry is clamped to the token's exp (RFC 7662) when present, so the staleness window never outlives the token itself.