ci: add validation workflow for maintainers list

We need to make sure that we don't insert invalid maintainers otherwise
it breaks the RFC39 invite workflow. Check that we have valid nix and
the required attributes are able to be parsed properly.

Signed-off-by: Austin Horstman <khaneliman12@gmail.com>

.github/workflows/validate-maintainers.yml

@@ -0,0 +1,91 @@
+name: Validate maintainers.nix
+on:
+  pull_request:
+    paths: ["modules/lib/maintainers.nix"]
+  workflow_dispatch:
+    inputs:
+      run_tests:
+        description: 'Run validation tests'
+        required: false
+        default: true
+        type: boolean
+jobs:
+  validate-maintainers:
+    runs-on: ubuntu-latest
+    if: github.repository_owner == 'nix-community'
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+      - name: Get Nixpkgs revision from flake.lock
+        id: get-nixpkgs
+        run: |
+          echo "rev=$(jq -r '.nodes.nixpkgs.locked.rev' flake.lock)" >> "$GITHUB_OUTPUT"
+      - name: Install Nix
+        uses: cachix/install-nix-action@v31
+        with:
+          nix_path: nixpkgs=https://github.com/NixOS/nixpkgs/archive/${{ steps.get-nixpkgs.outputs.rev }}.tar.gz
+      - name: Validate Nix syntax
+        run: |
+          echo "🔍 Validating maintainers.nix syntax..."
+          if nix eval --file modules/lib/maintainers.nix --json > /dev/null; then
+            echo "✅ Valid Nix syntax"
+          else
+            echo "❌ Invalid Nix syntax"
+            exit 1
+          fi
+      - name: Validate maintainer entries
+        run: |
+          echo "🔍 Validating maintainer entries..."
+          python3 -c "
+          import json
+          import re
+          import subprocess
+          import sys
+
+          # Get the maintainers data from the Nix file
+          result = subprocess.run(['nix', 'eval', '--file', 'modules/lib/maintainers.nix', '--json'],
+                                 capture_output=True, text=True, check=True)
+          maintainers = json.loads(result.stdout)
+          errors = []
+
+          for name, data in maintainers.items():
+            # Check REQUIRED fields - github and githubId are mandatory
+            if 'github' not in data:
+              errors.append(f'{name}: Missing required field \"github\"')
+            if 'githubId' not in data:
+              errors.append(f'{name}: Missing required field \"githubId\"')
+
+            # Validate GitHub ID is a positive integer (NOT a string)
+            if 'githubId' in data:
+              github_id = data['githubId']
+              if not isinstance(github_id, int):
+                errors.append(f'{name}: githubId must be a number, not a string: {github_id} (type: {type(github_id).__name__})')
+              elif github_id <= 0:
+                errors.append(f'{name}: githubId must be positive: {github_id}')
+
+          if errors:
+            print('❌ Validation errors found:')
+            for error in errors:
+              print(f'  - {error}')
+            sys.exit(1)
+          else:
+            print('✅ All maintainer entries are valid')
+            print(f'✅ Validated {len(maintainers)} maintainer entries')
+          "
+      - name: Test generation
+        if: inputs.run_tests == true
+        run: |
+          echo "🔍 Testing all-maintainers.nix generation..."
+          ./lib/python/generate-all-maintainers.py
+
+          echo "🔍 Validating generated file..."
+          if nix eval --file ./all-maintainers.nix --json > /dev/null; then
+            echo "✅ Generated file has valid Nix syntax"
+          else
+            echo "❌ Generated file has invalid Nix syntax"
+            exit 1
+          fi
+      - name: Summary
+        run: |
+          echo "✅ All validation checks passed!"
+          echo "📋 The maintainers.nix file is ready for merge"