message: refactor(aio): provide fallback values for secrets (useful during dev)
diff: set -eu -o pipefail
  # Set up env variables for production
  -export AIO_GITHUB_TOKEN=$(head -c -1 /aio-secrets/GITHUB_TOKEN 2>/dev/null)
  -export AIO_PREVIEW_DEPLOYMENT_TOKEN=$(head -c -1 /aio-secrets/PREVIEW_DEPLOYMENT_TOKEN 2>/dev/null)
  +export AIO_GITHUB_TOKEN=$(head -c -1 /aio-secrets/GITHUB_TOKEN 2>/dev/null || echo "MISSING_GITHUB_TOKEN")
  +export AIO_PREVIEW_DEPLOYMENT_TOKEN=$(head -c -1 /aio-secrets/PREVIEW_DEPLOYMENT_TOKEN 2>/dev/null || echo "MISSING_PREVIEW_DEPLOYMENT_TOKEN")
  # Start the upload-server instance
  # TODO(gkalpak): Ideally, the upload server should be run as a non-privileged user.
  