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.interface.ts

@@ -13,5 +13,6 @@ export interface IUser extends Document {
     type: UserType,
     lastLogin: Date,
     twoFASecret?: string,
+    brokerToken: string,
     createdAt?: Date
 }