[BUG] merge-similar-caches can't discover caches when using BuildJet backend

[deemp]

Describe the bug

Individual caches were created:

• https://github.com/nix-community/cache-nix-action/actions/runs/8902930565/job/24449803561#step:15:27
• https://github.com/nix-community/cache-nix-action/actions/runs/8902930565/job/24449803693#step:15:27

However, they weren't discovered:

• https://github.com/nix-community/cache-nix-action/actions/runs/8902930565/job/24449974304#step:5:29

To Reproduce

Run "Nix CI with BuildJet backend" at this commit.

Expected behavior

merge-similar-caches discovers individual caches and restores them.

Context

We use a custom cache package for the BuildJet backend (link). This package comes from BuildJet/toolkit synchronized with actions/toolkit.

The action tries to restore all caches with matching prefixes (link) and calls octokit (link). However, octokit can't see caches created by BuildJet.

We need a way to interact with BuildJet caches.

• list them (for this to work)
• purge them (for this to work)

The problem is that BuildJet didn't update the github package (link).