Update Django version to 4.2 (LTS) and Python to 3.12 in Django example

[weslord]

Django 3.2 and Python 3.7 are no longer supported.

I also ran django-admin startproject to update the project files.

The diff looks hairier than it is. Most of the lines are startproject updating the version number in comments.

Here are the concrete changes:

• URL config uses path() instead of url() (this is the only breaking change)
• Settings uses pathlib.Path instead of path.join
• Added new ASGI config
• DEFAULT_AUTO_FIELD = 'django.db.models.BigAutoField'