networking.wireguard: generate leaner units

[teto]

Description of changes

Just a refacto to remove newlines from the ExecStart of the generated unit in systemctl cat wireguard-wg.service
Before:

$ cat /nix/store/shkicpczsrwlz2dyp6wg7k0sqxklzhif-unit-script-wireguard-wg-start/bin/wireguard-wg-start
#!/nix/store/5lr5n3qa4day8l1ivbwlcby2nknczqkq-bash-5.2p26/bin/bash
set -e
modprobe wireguard || true



ip link add dev "wg" type wireguard



ip address add "10.100.0.2/24" dev "wg"

wg set "wg" private-key "myredacted.key" listen-port "51820"

ip link set up dev "wg"

after

➜ cat /nix/store/47l9if51z4klh1lx6vfmkhjyr9jkpr71-unit-script-wireguard-wg-start/bin/wireguard-wg-start
#!/nix/store/5lr5n3qa4day8l1ivbwlcby2nknczqkq-bash-5.2p26/bin/bash
set -e

modprobe wireguard || true
ip link add dev "wg" type wireguard
ip address add "10.100.0.2/24" dev "wg"
wg set "wg" private-key "myredacted.key" listen-port "51820"
ip link set up dev "wg"

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandboxing enabled in nix.conf? (See Nix manual)
  • sandbox = relaxed
  • sandbox = true
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 24.05 Release Notes (or backporting 23.05 and 23.11 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
• Fits CONTRIBUTING.md.

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[teto]

@SEIAROTg since you've touched this recently

[SEIAROTg]

LGTM.

I feel the original string interpolation is slightly more readable though. Can we do something like this instead?

script = pipe ''
   # original code
'' [(split "\n+") (filter isString) (concatStringsSep "\n")]