MVP for Package registry API

[blaix]

• Register a new user, or login
• Register a publishing identity (gren-lang is a publishing identity, me@example.com is a user) (completed in Create publishing identities #29 and Publishing identity cleanup #38)
• Publish new packages/versions
• Ask which version is latest for a given compiler version, and which was the previous version related to some version number.
• Refresh tokens?
• VictoriaLogs compatible logging. This would make it easy to monitor the new registry on grafana.gren-lang.org. This is how the existing registry does it: https://github.com/gren-lang/package.gren-lang.org/blob/main/src/log.js
• Misc TODOs in README and code.

[robinheghan]

Since we're using the term "MVP" here, might I suggest that the following bullet points are moved to a later milestone?

• Add or remove additional users to a publishing identity
• Permissions in a publishing identity (only download, publish new packages, user admin)
• Revoke a package/version (the name/version is still registered, but the actual content is removed).

[robinheghan]

I'd also like to nominate the following bullet point:

• VictoriaLogs compatible logging. This would make it easy to monitor the new registry on grafana.gren-lang.org. This is how the existing registry does it: https://github.com/gren-lang/package.gren-lang.org/blob/main/src/log.js

[blaix]

Agree with those points. Will update the issues soon.

[blaix]

Updated the issues accordingly (a while back, but forgot to update here)