Checksum and .asc files beside a versioned artifact are as immutable as the
artifact, but were routed through the metadata path: uncached until a
first successful fetch, with no retry or circuit breaker. A build pulling
hundreds of artifacts sent as many checksum requests straight to Maven
Central, which rate-limited the proxy, after which every further checksum
request still went upstream and failed.
Only maven-metadata.xml and its own checksums stay on the metadata path,
since the version listing changes with each release.
The Maven handler cached only .jar, .war, .ear, .pom, .aar, .klib and
.module files, so distributions published as archives, such as
apache-maven-{version}-bin.tar.gz, were proxied uncached on every request.
.zip, .tar.gz, .tgz, .tar.bz2 and .tar.xz files now go through the artifact
cache like other artifacts.
Co-authored-by: Giles Westwood <201443+gilesw@users.noreply.github.com>
