当在名为“bookings”的应用中创建联系人时，我想在名为“core”的单独应用中创建用户。我在配置信号以处理此问题时遇到问题。
目前，我正在使用信号检查User是否存在，并将现有User分配给Contact示例或创建新User并进行分配。
我尝试将用户属性设置为允许null和blank等，但一直收到以下警告：
完整性/bookings/contacts处的错误/关系“bookings_contact”的列“user_id”中的空值违反了非空约束详细信息：失败行包含（18，tesing@testing.com，5555555，空）。
bookings.models.py

from django.db import models
from django.conf import settings
from django.contrib import admin
import datetime

# Create your models here.

class Contact(models.Model):
    email = models.EmailField(max_length=255, null=True, blank=True)
    phone = models.CharField(max_length=255, null=False, blank=True)
    user = models.OneToOneField(settings.AUTH_USER_MODEL, on_delete=models.CASCADE, null=False, blank=True)

core.models.py

from django.contrib.auth.models import AbstractUser
from django.db import models

"""
Creating a User in Core app to decuple the core app from the bookings app.
Email UNIQUE constraint handled in serializers.py and admin.py
"""

class User(AbstractUser):
    email = models.EmailField(unique=True)

core.signals.handlers.py

from django.db.models.signals import post_save
from django.dispatch import receiver
from django.utils.crypto import get_random_string

from bookings.models import Contact
from core.models import User

@receiver(post_save, sender=Contact)
def create_user_for_new_contact(sender, instance, created, **kwargs):
    if created and instance.email:
        email = instance.email
        try:
            user = User.objects.get(email=email)
        except User.DoesNotExist:
            password = get_random_string(length=12)
            user = User.objects.create(email=email, password=password)
        instance.user = user
        instance.save()

core.apps.py

from django.apps import AppConfig

class CoreConfig(AppConfig):
    default_auto_field = 'django.db.models.BigAutoField'
    name = 'core'

    def ready(self) -> None:
        import core.signals.handlers