Use cached_db sessions by default

[pyanderson]

Description

This PR improves the backend session setup by configuring Django to use Redis as the default cache and cached_db
as the session engine, bringing the application closer to its intended runtime behavior. It also improves
development visibility by enabling more detailed Gunicorn access logs, making it easier to inspect requests and
debug backend behavior locally. Since the new session setup introduces a cache dependency, the test configuration
was updated to use an in-memory cache to keep tests isolated and independent from Redis.

Motivation and Context

The changes in this PR are grouped because they all support the same backend infrastructure improvement:

1. Session/cache setup: configure Redis as the default Django cache and switch sessions to cached_db.
2. Developer visibility: improve Gunicorn access logging in development to make request behavior easier to
   inspect.
3. Test isolation: override the cache backend in tests to use in-memory storage instead of Redis.

Overall, this brings development and runtime behavior closer together while keeping the test environment
lightweight and deterministic.

Screenshots (if appropriate):

N/A

Steps to reproduce (if appropriate):

• Create a new project using this branch as the template:

django-admin startproject new_styling --extension py,json,yml,yaml,toml --name Dockerfile,README.md,.env.example,.gitignore,Makefile,.npmrc --template=https://github.com/vintasoftware/django-react-boilerplate/archive/refs/heads/560-use-cache-db-sessions-by-default.zip

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires documentation updates.
• I have updated the documentation accordingly.
• My change requires dependencies updates.
• I have updated the dependencies accordingly.

Closes #560

[fjsj]

I think Redis is unnecessary here? cached_db means using the DB as cache, not Redis.

[pyanderson]

I think Redis is unnecessary here? cached_db means using the DB as cache, not Redis.

cached_db doesn't mean “use the DB as cache”. It means sessions are persisted in the database, with a
cache layer in front for performance.

That cache layer does not have to be Redis specifically. It could also be DatabaseCache, Memcached, or
local-memory, but Django generally recommends Redis or Memcached for production and discourages
local-memory cache in multi-process setups

https://docs.djangoproject.com/en/5.2/topics/http/sessions/#using-cached-sessions

Warning
You should only use cache-based sessions if you’re using the Memcached or Redis cache backend. The local-memory cache backend doesn’t retain data long enough to be a good choice, and it’ll be faster to use file or database sessions directly instead of sending everything through the file or database cache backends. Additionally, the local-memory cache backend is NOT multi-process safe, therefore probably not a good choice for production environments.

[fjsj]

Yep, I got confused, but what I wanted was what we had in other simple projects by using locmem. I see docs now don't recommend locmem, as you quoted: "The local-memory cache backend doesn’t retain data long enough to be a good choice, and it’ll be faster to use file or database sessions directly instead of sending everything through the file or database cache backends.". So I guess the best is to drop this. In general having Redis as a failure-point to get some little performance gain is not the best option for most projects. Thanks anyway for the PR! Dropping it.