BUILD-756 Migrate dogfood merge task to GH actions

.github/workflows/dogfood.yml

@@ -0,0 +1,29 @@
+name: Dogfood merge
+on:
+  push:
+    branches:
+      - master
+      - "dogfood/**"
+  delete:
+    branches:
+      - "dogfood/**"
+jobs:
+  dogfood_merge:
+    # prevent job to run on public repository sonarsource/sonarqube
+    if: github.repository == 'sonarsource/sonar-enterprise'
+    runs-on: ubuntu-latest
+    name: Update dogfood-on-next branch
+    steps:
+      - name: Merge dogfood and master branches
+        uses: SonarSource/gh-action_dogfood_merge@1
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_ORG_TOKEN }}
+        with:
+          dogfood-branch: "dogfood-on-next"
+      - name: Notify failures on Slack
+        if: failure()
+        uses: Ilshidur/action-slack@2.0.0
+        env:
+          SLACK_WEBHOOK: ${{ secrets.SLACK_WEBHOOK }}
+        with:
+          args: "Failed to merge dogfood and master branches, see the logs at https://github.com/SonarSource/sonar-enterprise/actions"