如何通过信号在Django中创建通知系统

from django.dispatch import receiver
from django.db.models.signals import post_save
from django.contrib.auth.models import User
from django.contrib.messages import get_messages
from django.contrib.messages import constants as messages
from django.contrib.messages.api import MessageFailure

from django.db import models

class Notification(models.Model):
    user = models.ForeignKey(User, on_delete=models.CASCADE)
    message = models.CharField(max_length=255)
    created_at = models.DateTimeField(auto_now_add=True)
    is_read = models.BooleanField(default=False)

@receiver(post_save, sender=Notification)
def send_notification(sender, instance, created, **kwargs):
    if created:
        # 发送通知给用户
        # 可以使用第三方库或自定义方法发送通知，例如发送邮件或推送通知到移动设备
        pass

from django.db.models.signals import post_save
from django.dispatch import receiver
from django.contrib.auth.models import User
from django.contrib.messages import get_messages
from django.contrib.messages import constants as messages
from django.contrib.messages.api import MessageFailure

@receiver(post_save, sender=User)
def create_notification(sender, instance, created, **kwargs):
    if created:
        Notification.objects.create(user=instance, message='Welcome to our website!')