## Signals

### Signal Patterns

```python
# apps/users/signals.py
from django.db.models.signals import post_save
from django.dispatch import receiver
from django.contrib.auth import get_user_model
from .models import Profile

User = get_user_model()

@receiver(post_save, sender=User)
def create_user_profile(sender, instance, created, **kwargs):
    """Create profile when user is created."""
    if created:
        Profile.objects.create(user=instance)

@receiver(post_save, sender=User)
def save_user_profile(sender, instance, **kwargs):
    """Save profile when user is saved."""
    instance.profile.save()

# apps/users/apps.py
from django.apps import AppConfig

class UsersConfig(AppConfig):
    default_auto_field = 'django.db.models.BigAutoField'
    name = 'apps.users'

    def ready(self):
        """Import signals when app is ready."""
        import apps.users.signals
```