如何在Django中确定用户何时有空闲超时？

from django.db import models
from django.contrib.auth.models import AbstractBaseUser, BaseUserManager

class CustomUserManager(BaseUserManager):
    pass

class CustomUser(AbstractBaseUser):
    email = models.EmailField(unique=True)
    last_activity = models.DateTimeField(auto_now=True)

    objects = CustomUserManager()

    USERNAME_FIELD = 'email'

from django.http import HttpResponse

class LastActivityMiddleware:
    def __init__(self, get_response):
        self.get_response = get_response

    def __call__(self, request):
        if request.user.is_authenticated:
            request.user.last_activity = timezone.now()
            request.user.save(update_fields=['last_activity'])

        response = self.get_response(request)
        return response

MIDDLEWARE = [
    # ...
    'myapp.middleware.LastActivityMiddleware',
    # ...
]

from django.core.management.base import BaseCommand
from django.utils import timezone
from myapp.models import CustomUser

class Command(BaseCommand):
    def handle(self, *args, **options):
        idle_timeout = 30 * 60  # 30 minutes
        idle_users = CustomUser.objects.filter(last_activity__lte=timezone.now() - timezone.timedelta(seconds=idle_timeout))

        for user in idle_users:
            # 执行相应的操作，例如将用户从在线状态更改为离线状态
            user.is_online = False
            user.save(update_fields=['is_online'])