packages: APT repo in R2

[alltilla]

Depends on #107

Example config:

storage:
  vendor: "s3"
  incoming:
    all:
      endpoint: "https://foobar.r2.cloudflarestorage.com"
      bucket: "axosyslog-apt-incoming"
      access-key: "foobar"
      secret-key: "foobar"
  indexed:
    all:
      endpoint: "https://foobar.r2.cloudflarestorage.com"
      bucket: "axosyslog-apt-indexed"
      access-key: "foobar"
      secret-key: "foobar"

cdn:
  vendor: "cloudflare"
  all:
    zone-id: "foobar"
    api-token: "foobar"

gpg-key-path: "/home/runner/work/axosyslog/axosyslog/packaging/package-indexer/axosyslog_signing_key.sub.priv.asc"

Example run: https://github.com/alltilla/axosyslog/actions/runs/9147374885

[MrAnno]

TODO:

• an AxoSyslog PGP key (certify-only master key + sign-only subkey)
• store signing subkey as a secret
• public R2 bucket on a subdomain, access keys stored as a secret
• public signing key shared on subdomain
• (+ optionally on https://keys.openpgp.org)
• update PR with all the above
• re-enable package upload in draft-release