ci: replace auto-merge with github script

ref https://docs.github.com/en/code-security/dependabot/working-with-dependabot/automating-dependabot-with-github-actions#approve-a-pull-request

Signed-off-by: Marvin <7430964+marpme@users.noreply.github.com>

Author: marpme

.github/workflows/depsmerge.yml

@@ -1,16 +1,27 @@
-name: auto-merge
+name: Dependabot Auto-Merge
+on: pull_request
 
-on:
-  pull_request:
-    branches:
-      - main
+permissions:
+  pull-requests: write
 
 jobs:
-  auto-merge:
+  dependabot-merge:
     runs-on: ubuntu-latest
+    if: ${{ github.actor == 'dependabot[bot]' }}
     steps:
-      - uses: actions/checkout@v3
-      - uses: ahmadnassri/action-dependabot-auto-merge@v2
+      - name: Dependabot metadata
+        id: metadata
+        uses: dependabot/fetch-metadata@v1
         with:
-          target: minor
-          github-token: ${{ secrets.AUTO_MERGE_TOKEN }}
+          github-token: "${{ secrets.GITHUB_TOKEN }}"
+      - name: Approve a PR
+        run: gh pr review --approve "$PR_URL"
+        env:
+          PR_URL: ${{github.event.pull_request.html_url}}
+          GITHUB_TOKEN: ${{secrets.GITHUB_TOKEN}}
+      - name: Enable auto-merge for Dependabot PRs
+        if: ${{ steps.metadata.outputs.update-type == 'version-update:semver-minor' }}
+        run: gh pr merge --auto --merge "$PR_URL"
+        env:
+          PR_URL: ${{github.event.pull_request.html_url}}
+          GITHUB_TOKEN: ${{secrets.GITHUB_TOKEN}}