Ruby builds fetch gems from rubygems.org directly because artifactapi has no RubyGems remote type.
- add `gems` package type proxying `https://rubygems.org`-style sources
- treat `versions`, `names`, `info/*` and `*specs.4.8.gz` as mutable, `gems/*.gem` and `quick/Marshal.4.8/*.gemspec.rz` as immutable
- serve `api/v1/*.json` as `application/json`
- add a gem/bundler usage snippet to the UI and a gems e2e caching case
Requires unkin/artifactapi#148 (HEAD route; RubyGems probes `HEAD /versions`).
Reviewed-on: #142
Co-authored-by: unkin-agent <unkin-agent@unkin.net>
Co-committed-by: unkin-agent <unkin-agent@unkin.net>
unkin-agent