add tf formatting workflow

.github/workflows/tf_formatting.yml

@@ -0,0 +1,35 @@
+# Runs auto-formatting script on push to any branch
+name: "Run terraform formatting"
+
+permissions:
+  id-token: write
+  contents: write
+
+on: push
+
+jobs:
+  autoformat:
+    name: autoformat
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out project
+        uses: actions/checkout@v4
+
+      - name: terraform fmt
+        uses: dflook/terraform-fmt@v1
+
+      - name: Check for formatting changes
+        id: check_formatting_changes
+        run: |
+          if [[ -n $(git status --porcelain) ]]; then
+              echo "changes=true" >> "$GITHUB_OUTPUT"; 
+          fi
+
+      - name: Commit and push formatting changes
+        if: steps.check_formatting_changes.outputs.changes == 'true'
+        run: |
+          git config user.name "Github on behalf of Wellcome Collection"
+          git config user.email "wellcomedigitalplatform@wellcome.ac.uk"
+          git commit -am "Apply auto-formatting rules"
+          git push
+