Logging and minor code improvements

[avnik]

Description

More flexible control on logging, also more excessive logging in debug mode.
Also contains minor code improvements

Checklist

• Summary of the proposed changes in the PR description
• More detailed description in the commit message(s)
• Commits are squashed into relevant entities - avoid a lot of minimal dev time commits in the PR
• Contribution guidelines followed
• Test procedure added to nixos/tests
• Author has run nix flake check --accept-flake-config and it passes
• All automatic Github Action checks pass - see actions
• Author has added reviewers and removed PR draft status

Testing

Log controlled by GIVC_LOG variable, as well as givc.admin.debug = true option.
Debug logging turned on in tests