nixos/webhook: unable to use sockets

[AndrewKvalheim]

Describe the bug

The recent update to pkgs.webhook included:

• Add option to bind to a Unix socket instead of a TCP port (#703)
• Add support for systemd socket activation (#704)

but services.webhook doesn’t expose any way to use this.

Expected behavior

• Some way to specify -socket instead of -ip and -port
• The generated systemd.services.webhook.script should be compatible with socket activation

Additional context

Reference: Using systemd socket activation

Metadata

$ nix-shell --packages 'nix-info' --run 'nix-info --markdown'
 - system: `"x86_64-linux"`
 - host os: `Linux 6.6.63, NixOS, 24.11 (Vicuna), 24.11.710194.f9f0d5c5380b`
 - multi-user?: `yes`
 - sandbox: `yes`
 - version: `nix-env (Nix) 2.24.10`
 - channels(root): `"nixos-24.11, nixos-hardware, unstable"`
 - nixpkgs: `/nix/var/nix/profiles/per-user/root/channels/nixos`

Notify maintainers

@W95Psp @ncfavier @azahi

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