multiple realms fix (#102)

* Allow to use multiple realms

This change is a ressurection of PR #88 which can't be merged due to significant refactor of the codebase.

* Fix the autocleanup routine to handle multiple realms correctly, update tests.

* Metadata rediscovery when provider is unavailable for any reason during the start.

This one prevents the permanent 503 from the plugin when OIDC provider was for some reason unavailable during the start.

utilities.go

@@ -3,6 +3,8 @@
 package traefikoidc
 
 import (
+	"crypto/sha256"
+	"encoding/hex"
 	"encoding/json"
 	"fmt"
 	"html"
@@ -222,8 +224,13 @@ func (t *TraefikOidc) Close() error {
 		rm := GetResourceManager()
 
 		// Stop singleton tasks related to this instance
-		_ = rm.StopBackgroundTask("singleton-token-cleanup")    // Safe to ignore: best effort cleanup
-		_ = rm.StopBackgroundTask("singleton-metadata-refresh") // Safe to ignore: best effort cleanup
+		_ = rm.StopBackgroundTask("singleton-token-cleanup") // Safe to ignore: best effort cleanup
+		// Stop metadata refresh task using same hash-based name as startMetadataRefresh
+		if t.providerURL != "" {
+			hash := sha256.Sum256([]byte(t.providerURL))
+			taskName := "singleton-metadata-refresh-" + hex.EncodeToString(hash[:])[0:6]
+			_ = rm.StopBackgroundTask(taskName) // Safe to ignore: best effort cleanup
+		}
 
 		// Remove reference for this instance
 		rm.RemoveReference(t.name)