Real-time communication with frontend

- Frontend shows heatmap of most visit places
- Maximum accuracy can now be set
- Fix bug where battery chart filtered values wrongly

backend/models/user/user.schema.ts

@@ -6,6 +6,7 @@ const schemaUser = new Schema({
     salt: { type: String, required: true },
     type: { type: String, required: true, default: 'user' },    // This could be user, admin, guest
     twoFASecret: { type: String, required: false },
+    brokerToken: { type: String, required: true },
     lastLogin: { type: Date, required: true, default: Date.now },
 }, {
     timestamps: {