ConCache-backed implementation of Atex.ServiceAuth.JTICache.

Each jti is stored with a per-item TTL derived from the token's own exp claim, so entries are evicted automatically once the corresponding token could no longer be presented as valid. This keeps memory use proportional to the number of currently-live tokens rather than growing without bound.

The TTL check interval defaults to 30 seconds and can be overridden:

config :atex, Atex.ServiceAuth.JTICache.ETS, ttl_check_interval: :timer.seconds(10)