bootc install does not use my podman credentials

I've tried to install a bootable container with an ```install to-filesystem``` as documented here: https://containers.github.io/bootc/bootc-install.html#executing-bootc-install

My image is pushed in a private registry tag (in quay.io). However bootc cannot access my repository. I used ```podman login quay.io``` to login on the host, which allows ```podman``` to pull the container image, but for some reason that I cannot understand ```bootc``` wants to access it again:

```
# sudo podman run --rm --privileged --pid=host --security-opt label=type:unconfined_t -v /:/target -v /var/lib/containers:/var/lib/containers quay.io/swalter/tuesday:1.0 bootc install to-filesystem --karg=console=ttyS0,115200n8 --replace=alongside /target
Trying to pull quay.io/swalter/tuesday:1.0...
Getting image source signatures
Copying blob 123a23fee02f done
Copying blob 123a23fee02f done
... snip ...
Copying blob f76da783556e done
Copying config 4787122538 done
Writing manifest to image destination
ERROR Installing to filesystem: Verifying fetch: Creating importer: Failed to invoke skopeo proxy method OpenImage: remote error: reading manifest 1.0 in quay.io/swalter/tuesday: unauthorized: access to the requested resource is not authorized
```

Start with the documented install-to-filesystem flow at https://containers.github.io/bootc/bootc-install.html#executing-bootc-install and reproduce the command using podman login quay.io and the mounted /var/lib/containers. Trace why the second image access reaches the skopeo proxy and compare credential visibility; done means a private quay.io image installs without the unauthorized manifest error.

Scritto dal modello di indicizzazione a partire dal testo della issue.