A Debian package was cached under its repository and file name, but
fetched from its full path. Docker's apt repository has a pool under each
suite with the same file names, so a bookworm client could get the
bullseye build that was fetched first, and fail its hash check. Packages
are now cached under their path.
Conan joined revision, package reference, package revision and file name
with underscores, which revisions can contain, so a recipe file and a
package file could share a cache entry. The parts are now joined with
slashes.
Entries cached under the old names are still served, but only for the
URL they were fetched from, so warm caches keep working.
Since #431 the handler stores Conan archives under pkg:conan/{name} with the version as the version and the revisions and any user/channel in the filename. purl keeps conan names as they are, so package rules use the default mapping, and pkg:conan/zlib covers every version, revision and user/channel of the recipe.
The mirror can't fetch conan packages, so there's no mirror test.
Refs #306
