Expired PGP Key on puppet PPA

Describe the Bug

Unable to install puppet agent over apt. The PGP Key used for signing on apt.puppet.com expired on Sunday 2025-04-06.

Steps to Reproduce

Steps to reproduce the behavior:

$ apt-get update && apt-get install puppet-agent -y
Hit:1 http://deb.debian.org/debian bookworm InRelease
Get:2 http://apt.puppet.com/ bookworm InRelease [56.5 kB]
Hit:3 http://deb.debian.org/debian bookworm-updates InRelease
Hit:4 http://deb.debian.org/debian-security bookworm-security InRelease
Err:2 http://apt.puppet.com/ bookworm InRelease
  The following signatures were invalid: EXPKEYSIG 4528B6CD9E61EF26 Puppet, Inc. Release Key (Puppet, Inc. Release Key) <release@puppet.com>
Reading package lists...
W: GPG error: http://apt.puppet.com/ bookworm InRelease: The following signatures were invalid: EXPKEYSIG 4528B6CD9E61EF26 Puppet, Inc. Release Key (Puppet, Inc. Release Key) <release@puppet.com>
E: The repository 'http://apt.puppet.com/ bookworm InRelease' is not signed.

Environment

• Platform [Debian 12, Ubuntu 24.04, and i guess all others as well]

No file or test is named in the issue. Start by reproducing the failure with apt-get update && apt-get install puppet-agent -y on a listed platform, then inspect the shell installer and its package-signing setup. Done means the Puppet repository signature validates and puppet-agent installs successfully without the expired-key error.