Notification system enhanced

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

backend/models/notifications/notification.schema.ts

@@ -0,0 +1,15 @@
+import { Schema, SchemaTypes } from 'mongoose';
+const schemaNotification = new Schema({
+    type: { type: String, required: true },
+    severity: { type: Number, required: true },
+    message: { type: Object, required: true },
+    user: { type: SchemaTypes.ObjectId }
+}, {
+    timestamps: {
+        createdAt: true,
+        updatedAt: false
+    },
+    versionKey: false
+});
+
+export { schemaNotification };