ci: add backport action

Signed-off-by: Paul Meyer <[email protected]>

.github/workflows/backport.yml

@@ -0,0 +1,35 @@
+name: backport pr
+
+on:
+  pull_request:
+    types: [labeled, closed]
+
+jobs:
+  backport:
+    name: Backport PR
+    runs-on: ubuntu-22.04
+    steps:
+      - name: Create backport config
+        run: |
+          cat <<EOF > .backportrc.json
+          {
+            "repoOwner": "edgelesssys",
+            "repoName": "nunki",
+            "branchLabelMapping": {
+              "^backport-to-(.+)$": "release/$1"
+            },
+            "fork": false
+          }
+          EOF
+      - name: Backport Action
+        uses: sorenlouv/backport-github-action@f7073a2287aefc1fa12685eb25a712ab5620445c # v9.3.1
+        with:
+          github_token: ${{ secrets.GITHUB_TOKEN }}
+      - name: Info log
+        if: success()
+        run: |
+          cat ~/.backport/backport.info.log
+      - name: Debug log
+        if: failure()
+        run: |
+          cat ~/.backport/backport.debug.log