Update OS version to Debian 12 (bookworm)

[4TT1L4]

Problem:

• Debian 11 (bullseye) is about to be transitioned to LTS support (August 14th, 2024), which is limited compared to the regular support for stable releases.

For further details please see:

• https://www.debian.org/releases/bullseye/

Solution:

• Update the OS version used in the Docker container to Debian 12 (bookworm), so we could profit from higher support level and faster security patching process.