chore: delete branch caches after merge

.github/workflows/clean-cache.yml

@@ -0,0 +1,27 @@
+name: cleanup caches by a branch
+on:
+    pull_request:
+        types:
+            - closed
+
+jobs:
+    cleanup:
+        runs-on: ubuntu-latest
+        steps:
+            - name: Cleanup
+              run: |
+                  echo "Fetching list of cache key"
+                  cacheKeysForPR=$(gh cache list --ref $BRANCH --limit 100 --json id --jq '.[].id')
+
+                  ## Setting this to not fail the workflow while deleting cache keys.
+                  set +e
+                  echo "Deleting caches..."
+                  for cacheKey in $cacheKeysForPR
+                  do
+                      gh cache delete $cacheKey
+                  done
+                  echo "Done"
+              env:
+                  GH_TOKEN: ${{ secrets.FREMTIND_BOT_ACCESS_TOKEN }}
+                  GH_REPO: ${{ github.repository }}
+                  BRANCH: refs/pull/${{ github.event.pull_request.number }}/merge