Backport #39782 by @basavaraj-sm05
The RubyGems compact index (the shared `/versions` file and per-package
`info/<name>` files) is line-based.
https://github.com/go-gitea/gitea/pull/38061 rejected line breaks in the
gem name, but the platform, dependency names and version requirements
from the gemspec still accepted them, letting an uploader forge index
lines for bundler clients.
The parser now rejects a line break in any of those fields. The Marshal
based endpoints are length prefixed and unaffected.
Co-authored-by: Basavaraj S m <basavaraj@digiscrypt.com>
Co-authored-by: silverwind <me@silverwind.io>