admin.py

from django.contrib import admin
from .models import *


class CustomerAdmin(admin.ModelAdmin):
    list_display = ['first_name', 'last_name', 'email', 'welcome_email_sent']
    list_display_links = ['first_name', 'last_name']


admin.site.register(Customer, CustomerAdmin)

apps.py

from django.apps import AppConfig


class CrmAppConfig(AppConfig):
    name = 'crm_app'

    def ready(self):
        import crm_app.signals

init.py

default_app_config = 'crm_app.apps.CrmAppConfig'

models.py

from django.db import models


class Customer(models.Model):
    first_name = models.CharField(max_length=100)
    last_name = models.CharField(max_length=100)
    email = models.EmailField(max_length=255)
    welcome_email_sent = models.DateTimeField(blank=True, null=True)
    created_at = models.DateTimeField(auto_now=True)

    def full_name(self):
        return f'{self.first_name} {self.last_name}'

    class Meta:
        db_table = "myawesomeapp_crm_customer"
        verbose_name = "Customer"
        verbose_name_plural = "Customers"

signals.py

from django.db.models.signals import post_save
from django.dispatch import receiver
from .models import *


@receiver(post_save, sender=Customer)
def send_welcome_email(sender, instance, created, *args, **kwargs):
    if created:
        pass