use github app to dispatch event instead of a PAT

a PAT may expire

https://github.com/organizations/VSETH-GECO/settings/apps/geco-deployment

Author: fbuetler

.github/workflows/push.yaml

@@ -2,7 +2,7 @@ name: Create and publish a Docker image
 
 on:
   push:
-    branches: ['main']
+    branches: ["main"]
 
 env:
   REGISTRY: ghcr.io
@@ -36,10 +36,20 @@ jobs:
           tags: ${{ env.REGISTRY }}/vseth-geco/radius:${{ env.SHORT_SHA }}
           labels: ${{ steps.meta.outputs.labels }}
 
+      - name: Generate GitHub App Token
+        uses: actions/create-github-app-token@v2
+        id: app-token
+        with:
+          app-id: ${{ vars.GECO_DEPLOYMENT_APP_ID }}
+          private-key: ${{ secrets.GECO_DEPLOYMENT_APP_PRIVATE_KEY }}
+          owner: ${{ github.repository_owner }}
+          repositories: |
+            k8s
+
       - name: Update k8s repo
         uses: peter-evans/repository-dispatch@v3
         with:
-          token: ${{ secrets.PERSONAL_ACCESS_TOKEN }}
+          token: ${{ steps.app-token.outputs.token }}
           repository: VSETH-GECO/k8s
           event-type: radius
           client-payload: |