Add SQLite to Registry Server, it's ready to go now 🚀

[f-f]

As per title, with this PR we are ready to launch the Registry Server as our main entrypoint for package managers to issue package publishing requests.

This patch is quite large, but there are a few main themes:

• we add a SQLite database to the registry server, so that the API is able to work asynchronously. When an Operation is submitted to the server, the API will create a Job in the database, to which the processing of that Operation is associated. All the logs from that pipeline will be stored in the database, and package managers (or whatever else issued that Operation request) will be able to request those logs by their JobId. This enables a "realtime" flow, where package managers can "stream" logs from the remote pipeline as it happens. I'm quite pleased with this 🙂
• we add a whole bunch of Nix infrastructure (in addition to what was already in place), so that we can deploy the server easily on our DigitalOcean server with Colmena
• we add a CONTRIBUTING.md documenting the Nix setup and more generally how to get started with contributing to the codebase
• and finally we add an integration test for the API pipeline itself

(this whole thing was coauthored with @thomashoneyman)

[f-f]

@thomashoneyman you might also want to take a look at the conflicts, the nix stuff in trunk does not go well with the new things

[f-f]

Also I have no idea why CI is failing - I suspect it's a problem in the npm package lock, but I just generated a fresh one 🤔

[thomashoneyman]

I can merge this with master and handle the Nix conflicts today!

[f-f]

We should squash-merge this with both of our usernames attached for the git blame

I've been doing this all along for the PRs where we both contributed 🙂