Modernise wagtail images

[ahayzen]

• [ ] Move to newer debian
• [ ] Move to pypi base or similar?
• [ ] Have CI test the images build and run
• [ ] Automate updating image
• [ ] Can we build static files into the image?

[ahayzen]

Static files can be reached via a named volume for an existing directory

eg

caddy:
  volumes:
    - static-data:/srv/site/static_data:ro

wagtail:
  volumes:
    - static-data:/mysite/static:ro

This would allow for /srv/site/static_data of caddy to be reading /mysite/static of wagtail.

https://www.digitalocean.com/community/tutorials/how-to-share-data-between-docker-containers#step-3-creating-a-volume-from-an-existing-directory-with-data