Reorganise GH workflows

Author: andreabedini

.github/workflows/format.yaml

@@ -7,6 +7,27 @@ on:
   pull_request:
 
 jobs:
+  format:
+    runs-on:
+      - ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install Nix
+        uses: DeterminateSystems/nix-installer-action@v4
+        with:
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+
+      - uses: DeterminateSystems/magic-nix-cache-action@v2
+
+      - uses: cachix/cachix-action@v12
+        with:
+           name: foliage
+           authToken: '${{ secrets.CACHIX_AUTH_TOKEN }}'
+
+      - run: nix develop --accept-flake-config --command fourmolu -m check .
+
   build:
     runs-on:
       - ubuntu-latest

.github/workflows/haskell.yml

@@ -11,17 +11,26 @@ jobs:
     steps:
       - name: Checkout repository
         uses: actions/checkout@v3
+
       - name: Install Nix
-        uses: cachix/install-nix-action@v19
+        uses: DeterminateSystems/nix-installer-action@v4
+        with:
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+
+      - uses: DeterminateSystems/magic-nix-cache-action@v2
+
+      - uses: cachix/cachix-action@v12
         with:
-          extra_nix_config: |
-            access-tokens = github.com=${{ secrets.GITHUB_TOKEN }}
+           name: foliage
+           authToken: '${{ secrets.CACHIX_AUTH_TOKEN }}'
+
       - name: Update flake.lock
         uses: DeterminateSystems/update-flake-lock@v16
         with:
           pr-title: "Update flake.lock" # Title of PR to be created
           pr-labels: |                  # Labels to be set on the PR
             dependencies
             automated
+
       - name: Print PR number
         run: echo Opened pull request ${{ steps.update.outputs.pull-request-number }}.