old_contents: from django.conf import settings
  from django.db import models
  from django.db.models.signals import post_save
  from django.dispatch import receiver
  
  
  class Profile(models.Model):
      user = models.OneToOneField(
          settings.AUTH_USER_MODEL, on_delete=models.CASCADE, related_name="profile"
      )
      bio = models.TextField(max_length=500, blank=True)
      address = models.CharField(max_length=255, blank=True)
      birth_date = models.DateField(null=True)
  
      class Meta:
          db_table = "profile"
  
      def __repr__(self):
          return f"<Profile id={self.id} username={self.user.username}>"
  
      def __str__(self):
          return f"Profile for user {self.user.username} w/ email: {self.user.email or 'N/A'}"
  
  
  @receiver(post_save, sender=settings.AUTH_USER_MODEL)
  def create_user_profile(sender, instance, created, **kwargs):
      if created:
          Profile.objects.create(user=instance)
  
  
  @receiver(post_save, sender=settings.AUTH_USER_MODEL)
  def save_user_profile(sender, instance, **kwargs):
      instance.profile.save()
  
new_contents: from django.conf import settings
  from django.db import models
  from django.db.models.signals import post_init, post_save
  from django.dispatch import receiver
  
  
  class Profile(models.Model):
      user = models.OneToOneField(
          settings.AUTH_USER_MODEL, on_delete=models.CASCADE, related_name="profile"
      )
      bio = models.TextField(max_length=500, blank=True)
      address = models.CharField(max_length=255, blank=True)
      birth_date = models.DateField(null=True)
  
      class Meta:
          db_table = "profile"
  
      def __repr__(self):
          return f"<Profile id={self.id} username={self.user.username}>"
  
      def __str__(self):
          return f"Profile for user {self.user.username} w/ email: {self.user.email or 'N/A'}"
  
  
  @receiver(post_save, sender=settings.AUTH_USER_MODEL)
  def create_or_update_user_profile(sender, instance, created, **kwargs):
      if created:
          Profile.objects.create(user=instance)
      instance.profile.save()
  
subject: Change model signals slightly