Support modern apt keyrings, required on Debian 13

Use Case

run docker on Debian 13 trixie

Notice: /Stage[main]/Docker::Repos/Apt::Source[docker]/Apt::Key[Add key: 9DC858229FC7DD38854AE2D88D81803C0EBFCD88 from Apt::Source docker]/Anchor[apt_key 9DC858229FC7DD38854AE2D88D81803C0EBFCD88 present]: Dependency Apt_key[Add key: 9DC858229FC7DD38854AE2D88D81803C0EBFCD88 from Apt::Source docker] has failures: true
Warning: /Stage[main]/Docker::Repos/Apt::Source[docker]/Apt::Key[Add key: 9DC858229FC7DD38854AE2D88D81803C0EBFCD88 from Apt::Source docker]/Anchor[apt_key 9DC858229FC7DD38854AE2D88D81803C0EBFCD88 present]: Skipping because of failed dependencies
Warning: /Stage[main]/Docker::Repos/Apt::Source[docker]/Apt::Setting[list-docker]/File[/etc/apt/sources.list.d/docker.list]: Skipping because of failed dependencies
Info: Class[Apt::Update]: Unscheduling all events on Class[Apt::Update]
Warning: /Stage[main]/Apt::Update/Exec[apt_update]: Skipping because of failed dependencies
Warning: /Stage[main]/Docker::Repos/Package[cgroupfs-mount]: Skipping because of failed dependencies
Warning: /Stage[main]/Docker::Install/Package[docker]: Skipping because of failed dependencies
Warning: /Stage[main]/Docker::Service/File[/etc/systemd/system/docker.service.d]: Skipping because of failed dependencies
Warning: /Stage[main]/Docker::Service/File[/etc/systemd/system/docker.service.d/service-overrides.conf]: Skipping because of failed dependencies
Warning: /Stage[main]/Docker::Service/Exec[docker-systemd-reload-before-service]: Skipping because of failed dependencies
Warning: /Stage[main]/Docker::Service/File[/etc/default/docker-storage]: Skipping because of failed dependencies
Warning: /Stage[main]/Docker::Service/File[/etc/default/docker]: Skipping because of failed dependencies
Info: Stage[main]: Unscheduling all events on Stage[main]
Error: Could not find a suitable provider for apt_key

Describe the Solution You Would Like

instead of:

deb [arch=amd64] https://download.docker.com/linux/debian bookworm stable

use

deb [arch=amd64,signed-by=/etc/apt/keyrings/debian.gpg] https://download.docker.com/linux/debian bookworm stable

Start with the Docker repository's Apt::Source[docker] and Apt::Key resources shown in the error report, and trace how the Docker apt source is configured. Compare the current source entry with the requested signed-by keyring form. Done means running Docker on Debian 13 no longer requires the unavailable apt_key provider and the repository can update successfully.