add convenient method to ProjectStateRegistry

Author: ywangd

server/src/main/java/org/elasticsearch/cluster/project/ProjectStateRegistry.java

@@ -54,6 +54,10 @@ public class ProjectStateRegistry extends AbstractNamedDiffable<Custom> implemen
     // A counter that is incremented each time one or more projects are marked for deletion.
     private final long projectsMarkedForDeletionGeneration;
 
+    public static ProjectStateRegistry get(ClusterState clusterState) {
+        return clusterState.custom(TYPE, EMPTY);
+    }
+
     public ProjectStateRegistry(StreamInput in) throws IOException {
         if (in.getTransportVersion().onOrAfter(TransportVersions.PROJECT_STATE_REGISTRY_ENTRY)) {
             projectsEntries = in.readMap(ProjectId::readFrom, Entry::readFrom);
@@ -97,6 +101,10 @@ public Settings getProjectSettings(ProjectId projectId) {
         return projectsEntries.getOrDefault(projectId, EMPTY_ENTRY).settings;
     }
 
+    public Set<ProjectId> getProjectsMarkedForDeletion() {
+        return projectsMarkedForDeletion;
+    }
+
     public boolean isProjectMarkedForDeletion(ProjectId projectId) {
         return projectsMarkedForDeletion.contains(projectId);
     }