update backport workflow and add auto-delete

Signed-off-by: David Cui <davidcui@amazon.com>

.github/workflows/backport.yml

@@ -1,16 +1,28 @@
 name: Backport
 on:
-  pull_request:
+  pull_request_target:
     types:
       - closed
       - labeled
 
 jobs:
   backport:
     runs-on: ubuntu-latest
+    permissions:
+      contents: write
+      pull-requests: write
     name: Backport
     steps:
+      - name: GitHub App token
+        id: github_app_token
+        uses: tibdex/github-app-token@v1.5.0
+        with:
+          app_id: ${{ secrets.APP_ID }}
+          private_key: ${{ secrets.APP_PRIVATE_KEY }}
+          installation_id: 22958780
+
       - name: Backport
-        uses: tibdex/backport@v1
+        uses: VachaShah/backport@v1.1.4
         with:
-          github_token: ${{ secrets.GITHUB_TOKEN }}
+          github_token: ${{ steps.github_app_token.outputs.token }}
+          branch_name: backport/backport-${{ github.event.number }}

.github/workflows/delete_backport_branch.yml

@@ -0,0 +1,15 @@
+name: Delete merged branch of the backport PRs
+on: 
+  pull_request:
+    types:
+      - closed
+
+jobs:
+  delete-branch:
+    runs-on: ubuntu-latest
+    if: startsWith(github.event.pull_request.head.ref,'backport/')
+    steps:
+      - name: Delete merged branch
+        uses: SvanBoxel/delete-merged-branch@main
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}