input: Write a function to create a Django application with a model that stores the name, address, and email of a user. The function should handle the creation of the Django project, the User model, and the migration process. If the Django project already exists, it should just create the User model and run the migrations.
  assert create_django_app('myapp')==True
  assert create_django_app('existing_app')==True
output: 
  def create_django_app(app_name):
      import os
      from pathlib import Path
      from django.core.management import call_command
      from django.core.management.commands.startapp import Command as StartAppCommand
      from django.core.management.commands.startproject import Command as StartProjectCommand
  
      project_path = Path(app_name)
      if not project_path.exists():
          StartProjectCommand().handle(app_name, app_name)
      
      os.chdir(app_name)
      StartAppCommand().handle('users', 'users')
      
      with open(f'users/models.py', 'w') as f:
          f.write("""
  from django.db import models
  
  class User(models.Model):
      name = models.CharField(max_length=100)
      address = models.CharField(max_length=200)
      email = models.EmailField(max_length=100)
  """)
      
      with open(f'{app_name}/settings.py', 'a') as f:
          f.write("\nINSTALLED_APPS += ['users']\n")
      
      call_command('makemigrations', 'users')
      call_command('migrate')
      
      return True
  