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.

autocleanup.go

@@ -266,18 +266,21 @@ func (cb *TaskCircuitBreaker) CanCreateTask(taskName string) error {
 	max := atomic.LoadInt32(&cb.maxConcurrent)
 
 	// For cleanup tasks, be more restrictive (singleton-like behavior)
+	// However, allow distinct realm-specific tasks (e.g., singleton-metadata-refresh-abc123 vs singleton-metadata-refresh-def456)
 	if strings.Contains(taskName, "cleanup") || strings.Contains(taskName, "singleton") {
 		cb.tasksMu.RLock()
-		hasCleanupTask := false
+		hasSameTask := false
 		for activeTask := range cb.activeTasks {
-			if strings.Contains(activeTask, "cleanup") || strings.Contains(activeTask, "singleton") {
-				hasCleanupTask = true
+			// Only block if the EXACT same task is already running
+			// This allows realm-specific tasks like singleton-metadata-refresh-{hash} to run concurrently
+			if activeTask == taskName {
+				hasSameTask = true
 				break
 			}
 		}
 		cb.tasksMu.RUnlock()
 
-		if hasCleanupTask {
+		if hasSameTask {
 			return fmt.Errorf("cleanup/singleton task already running: %s", taskName)
 		}
 	}