review fixes apr 2026 (#130)

* Multiple fixes

- refresh coordinator dedup + memory pressure wire
- middleware sse consolidation + timer leak + claim cache
- universal cache sync backfill + isDebug gate
- lazy background task race
- memory monitor stw cached + refresh() api

* fix(auth): suppress OIDC redirects on non-navigation requests

- [x] Add isNonNavigationRequest using Sec-Fetch-Mode and Accept headers
- [x] Add comprehensive TestIsNonNavigationRequest
- [x] Update ServeHTTP to 401 non-navigation and AJAX requests

Fixes #129

* feat(config): add custom CA and insecure skip verify for OIDC TLS

- [x] Add CACertPath, CACertPEM, InsecureSkipVerify to Config
- [x] Implement loadCACertPool for CA bundle loading
- [x] Update HTTPClientConfig with RootCAs and InsecureSkipVerify
- [x] Apply CA pool and skip verify to pooled HTTP clients
- [x] Enhance configKey to distinguish TLS configs
- [x] Add comprehensive ca_cert_test.go

Fixes #125

* feat(oidc): add custom CA certificate support for private OIDC providers

- [x] Add caCertPath, caCertPEM, insecureSkipVerify config options
- [x] Update traefik.yml with new OIDC client config fields
- [x] Add configuration schema descriptions for new options
- [x] Update README table and add Custom CA Certificates section

* Fix the documentation.

* test(redis): add oversized argument rejection test

- [x] Add TestRedisConn_RejectOversizedArgumentBytes
- [x] Import strings package

* Dependencies cleanup

docs/AUTH0_AUDIENCE_GUIDE.md

@@ -25,7 +25,10 @@ The **audience** (`aud`) claim in a JWT identifies the intended recipient of the
 
 ### Why Does This Matter?
 
-Proper audience validation prevents **token confusion attacks** where a token intended for one API is used to access another API.
+Audience validation rejects access tokens whose `aud` claim does not match the
+expected audience, blocking the trivial form of token confusion where a token
+issued for API A is presented to API B. (Defence in depth — pair with
+short-lived tokens, rotation, and per-API client credentials.)
 
 ---
 
@@ -137,8 +140,8 @@ http:
 **Recommended:** `true` for production
 
 **What it does:**
-- When `true`: Rejects sessions if access token audience doesn't match (prevents Scenario 2)
-- When `false`: Logs warnings but allows fallback to ID token (backward compatible)
+- When `true`: On audience mismatch, the middleware does **not** silently fall back to ID-token validation. It tries to refresh the access token first; if no refresh token is present (or refresh fails), the user is re-authenticated.
+- When `false`: Logs warnings and falls back to ID-token validation (backward compatible).
 
 **Example:**
 ```yaml
@@ -349,7 +352,7 @@ When opaque tokens are detected:
 
 **Cache behavior:**
 - Cache key: Token hash
-- TTL: 5 minutes or token expiry (whichever is shorter)
+- TTL: 5 minutes; if the token's `exp` is sooner, the cache entry expires at `exp` instead. Tokens without `exp` use the flat 5-minute TTL.
 - Reduces introspection requests for frequently used tokens
 
 ---