feat: NotificationServiceImpl init

at_client/src/main/java/org/atsign/client/api/impl/clients/NotificationServiceImpl.java

@@ -0,0 +1,65 @@
+package org.atsign.client.api.impl.clients;
+
+import java.util.List;
+import java.util.concurrent.CompletableFuture;
+
+
+import org.atsign.client.api.AtClient;
+import org.atsign.client.api.notification.AtNotification;
+import org.atsign.client.api.notification.NotificationParams;
+import org.atsign.client.api.notification.NotificationResult;
+import org.atsign.client.api.notification.NotificationService;
+import org.atsign.client.util.AtClientValidation;
+import org.atsign.common.AtSign;
+import org.atsign.common.NotificationStatus;
+
+public class NotificationServiceImpl implements NotificationService {
+
+    private final AtClient atClient;
+
+    public NotificationServiceImpl(AtClient atClient) {
+        this.atClient = atClient;
+    }
+
+    @Override
+    public CompletableFuture<Object> subscribe(String regex, boolean shouldDecrypt) {
+        throw new IllegalCallerException("Not implemented yet");
+    }
+
+    @Override
+
+    public CompletableFuture<NotificationResult> notify(NotificationParams params) {
+
+        return CompletableFuture.supplyAsync(() -> {
+            NotificationResult result = new NotificationResult(params.getNotificationId(), params.getAtKey(), NotificationStatus.undelivered);
+            if(params.getAtKey().sharedBy == null) {
+                params.getAtKey().sharedBy = atClient.getAtSign();
+            }
+
+            return result;
+        });
+
+
+    }
+
+    @Override
+    public CompletableFuture<NotificationResult> getStatus(String notificationId) {
+        throw new IllegalCallerException("Not implemented yet");
+    }
+
+    @Override
+    public CompletableFuture<List<AtNotification>> notifyList() {
+        throw new IllegalCallerException("Not implemented yet");
+    }
+
+    @Override
+    public CompletableFuture<NotificationResult> notifyDelete(String notificationId) {
+        throw new IllegalCallerException("Not implemented yet");
+    }
+
+    @Override
+    public CompletableFuture<NotificationResult> notifyDeleteAll() {
+        throw new IllegalCallerException("Not implemented yet");
+    }
+
+}