Follow-up to the OIDC security hardening, from a max-effort re-review:
- Refresh now re-checks the denylist immediately before minting, against the
(possibly remapped) identity but anchored on the original session `iat` — so a
back-channel logout / SCIM deny that lands during the IdP grant, or one
targeting the refreshed sub/sid, still blocks renewal instead of being escaped
by the renewed token's fresh iat. Completes the watermark revocation fix.
- SCIM PUT `userName` immutability check is now case-insensitive, matching the
case-insensitive list/create — a differently-cased userName echo no longer
400s "userName is immutable" and blocks deprovision. Completes the SCIM
case-insensitivity fix.
- Drop the unconditional state-cookie deletion on every callback exit: it let
one tab's callback clear another in-flight tab's cookie, breaking concurrent
logins. The cookie self-expires (max_age) and the Redis state is single-use,
so the delete wasn't needed.
Tests added for the refresh revocation re-check and the case-insensitive PUT.