Use pre-built Docker images to cut down installation times

[nikhilwoodruff]

I just did this with our PolicyEngine API package: basically, install once, then save the machine state and reinstall that in future actions. Here's our code. It cut about 10 minutes off deployment times.

(cc @rickecon @jdebacker )

[jdebacker]

@nikhilwoodruff - thanks for this suggestion.

One potential issue I see is that the Docker image can become stale and you might not find out that there are conflicts with your package and recent version of dependencies (GH Actions tests are often how I find out about such conflicts).

Am I understanding this correctly?

[nikhilwoodruff]

Yes- think it would need updating every so often but could still be a cut-down on time I think