ci(template): Install Nix in pre-commit workflow (#516)

* ci(template): Install Nix in pre-commit workflow

* Apply suggestions from code review

* chore: Extend comment about Nix version

* Apply suggestions from code review

---------

Co-authored-by: Nick <10092581+NickLarsenNZ@users.noreply.github.com>

Author: Techassi

config/versions.yaml

@@ -23,3 +23,10 @@ hadolint_version: v2.12.0
 # If you change the Python version here, make sure to also change it in
 # .github/workflows/pr_pre-commit.yml
 python_version: 3.12
+
+# This Nix version is used in the operators pre-commit workflow as they require
+# Nix to run some checks. Check for new versions here:
+# https://github.com/NixOS/nix/tags
+# Usually the latest version should just work and as such the version here can
+# be bumped without any constraints.
+nix_pkg_manager_version: 2.28.3

template/.github/workflows/pr_pre-commit.yaml.j2

@@ -6,6 +6,7 @@ on:
 
 env:
   CARGO_TERM_COLOR: always
+  NIX_PKG_MANAGER_VERSION: "{[ nix_pkg_manager_version }]"
   RUST_TOOLCHAIN_VERSION: "{[ rust_nightly_version }]"
   HADOLINT_VERSION: "{[ hadolint_version }]"
   PYTHON_VERSION: "{[ python_version }]"
@@ -29,3 +30,5 @@ jobs:
           python-version: ${{ env.PYTHON_VERSION }}
           rust: ${{ env.RUST_TOOLCHAIN_VERSION }}
           hadolint: ${{ env.HADOLINT_VERSION }}
+          nix: ${{ env.NIX_PKG_MANAGER_VERSION }}
+          nix-github-token: ${{ secrets.GITHUB_TOKEN }}