Currently, the multi-stage Docker build makes the `release` stage
inherit from `dependencies`, which will include any files created by the
`pip install` process in the final image.
By using `pip install --user` to make dependencies be installed in
`~/.local`, we can only copy those files into the final image, reducing
the image size:
```
cloudflare-ddns-fix-applied latest 68427bd7c88d 3 minutes ago 54.6MB
cloudflare-ddns-master latest 2675320b651d 8 minutes ago 65.9MB
```
A good resource going deeper on how this approach works can be found at
https://pythonspeed.com/articles/multi-stage-docker-python/, solution 1.
