fix issue with logout url (#112)

* fix(logout): handle logout requests before OIDC initialization

- [x] Add debug logging to logout handler entry point
- [x] Move logout path check before OIDC initialization to enable logout when provider unavailable
- [x] Move excluded URL and SSE checks before initialization wait
- [x] Add debug logging for initialization wait to diagnose hanging requests
- [x] Add test for logout functionality without OIDC provider availability

* feat(logout): implement OIDC backchannel and front-channel logout

- [x] Add logout token validation and backchannel logout handler
- [x] Add front-channel logout handler with iframe support
- [x] Implement session invalidation cache for distributed deployments
- [x] Add comprehensive logout token claim verification (issuer, audience, events, iat, sid/sub)
- [x] Integrate session invalidation checks into authorization flow
- [x] Add configuration options for enabling backchannel/front-channel logout
- [x] Add extensive test coverage for logout flows and edge cases
- [x] Update documentation with logout configuration examples
- [x] Add middleware routing for logout endpoints
- [x] Extend cache manager with session invalidation cache support

Resolves #110

* fixup! feat(logout): implement OIDC backchannel and front-channel logout

* fixup! Merge branch 'main' into fix-issue-with-logout-url

types.go

@@ -119,6 +119,8 @@ type TraefikOidc struct {
 	clientID                   string
 	clientSecret               string
 	registrationURL            string
+	backchannelLogoutPath      string
+	frontchannelLogoutPath     string
 	scopesSupported            []string
 	scopes                     []string
 	refreshGracePeriod         time.Duration
@@ -126,7 +128,10 @@ type TraefikOidc struct {
 	shutdownOnce               sync.Once
 	metadataRetryMutex         sync.Mutex
 	firstRequestMutex          sync.Mutex
+	sessionInvalidationCache   CacheInterface
 	minimalHeaders             bool
+	enableBackchannelLogout    bool
+	enableFrontchannelLogout   bool
 	firstRequestReceived       bool
 	requireTokenIntrospection  bool
 	metadataRefreshStarted     bool