.github: Use devcontainer to run Salt unit-tests

Author: TeddyAndrieux

.github/changed-files.yaml

@@ -39,6 +39,7 @@ unit-tests-storage-operator:
 unit-tests-salt:
   - salt/**
   - tox.ini
+  - .devcontainer/**
 
 unit-tests-lib-alert-tree:
   - tools/lib-alert-tree/**

.github/workflows/pre-merge.yaml

@@ -303,19 +303,28 @@ jobs:
         run: make test
 
   unit_tests_salt:
-    needs: changed-files
+    runs-on: ubuntu-latest
+    needs:
+      - build-devcontainer
+      - changed-files
+    container:
+      image: ghcr.io/${{ github.repository }}/devcontainer:${{ github.sha }}
+      # We have to use `root` for the moment
+      # Sees: https://github.com/actions/checkout/issues/1575
+      # Could work with a user with 1001 id but not for docker
+      options: --user root
+      credentials:
+        username: ${{ github.repository_owner }}
+        password: ${{ secrets.GITHUB_TOKEN }}
+    defaults:
+      run:
+        shell: bash
     if: needs.changed-files.outputs.unit-tests-salt == 'true'
-    runs-on: ubuntu-20.04
     steps:
       - name: Checkout
         uses: actions/checkout@v4
-      - name: Install Python 3.6
-        uses: actions/setup-python@v5
-        with:
-          python-version: "3.6"
-      - name: Install deps
-        run: |
-          pip install tox
+      - name: Set safe directory (since container is root and not user 1001)
+        run: git config --global --add safe.directory $GITHUB_WORKSPACE
       - name: Run all salt unit tests
         run: tox -e unit-tests