Allow adding labels to the packages

[dhirschfeld]

I uploaded my test eq-utils package to my energy-quants org but have to manually link it to the correct repository:

The package can be automatically linked to the correct repository if you add the label:

org.opencontainers.image.source https://github.com/OWNER/REPO

It might be nice to allow specifying one or more labels to be added to the package when uploading - e.g.

powerloader upload
    --label org.opencontainers.image.source=https://github.com/energy-quants/eq-utils
    --label org.opencontainers.image.version=$version
    <snip>

[dhirschfeld]

It seems the internal code allows annotations to be added to layers so I think all that is needed is to expose that to the cli. It looks like that would be done here:

powerloader/src/cli/main.cpp

Lines 427 to 430 in e6b10b0

	CLI::App* s_ul = app.add_subcommand("upload", "Upload a file");
	s_ul->add_option("files", du_files, "Files to upload");
	s_ul->add_option("-m", mirrors, "Mirror to upload to");
	s_ul->add_option("-f", file, "File from which to read mirrors, upload & download files");

...with the annotations plumbed through to OCILayer::from_file here:

powerloader/src/cli/main.cpp

Lines 168 to 173 in e6b10b0

	auto res
	= oci_upload(ctx,
	mirror,
	dest,
	elems[2],
	{ OCILayer::from_file("application/octet-stream", elems[0]) });

[dhirschfeld]

powerloader/src/uploader/oci_upload.cpp

Lines 53 to 55 in e6b10b0

	OCILayer OCILayer::from_file(const std::string& mime_type,
	const fs::path& file,
	const std::optional<nlohmann::json>& annotations)