The staging PR opened by github-actions-on-label-create.yml is currently
authored by the bot account behind STAGING_GITHUB_TOKEN, hiding the real
contributor on the staging side. Add a token-resolution step that, when
the PR author has stored a personal access token as repository secret
PAT_<LOGIN> (uppercase, '-' -> '_'), uses it to call the PR-creation API
so the staging PR is authored by them. Falls back to the bot token when
no per-user PAT is configured, preserving today's behavior.
Signed-off-by: Matt Liberty <mliberty@precisioninno.com>