Notification system enhanced

- Base for notifcation center
- Show text in map if no data is available

backend/models/notifications/notification.model.ts

@@ -0,0 +1,11 @@
+import { Model, model } from 'mongoose';
+import { IUser } from '../user/user.interface';
+import { INotification, ISeverity, NotificationType } from './notification.interface';
+import { schemaNotification } from './notification.schema';
+
+const modelNotification: Model<INotification> = model<INotification>('Notification', schemaNotification, 'Notification');
+export { modelNotification as Notification };
+
+export function addNotification(type: NotificationType, severity: ISeverity, message: any, user: IUser) {
+    return modelNotification.create({ type, severity, message, user });
+}