Function invalidate_cached_user 

pub(crate) async fn invalidate_cached_user(
    cache: &Cache,
    digest: &Digest,
    token_hmac_key: &SecretString,
)

Evicts a cached user mapping. Call this right after revoking a token so it can’t keep authenticating from a stale cache hit for the rest of its TTL.

Entries written before this keying scheme shipped are unreachable and only age out within MAX_CACHE_TTL.