Pin a deployment condition to the app that deployed

Anyone with the deployments: write permission on a repository can post a deployment status for any environment name, and two apps can deploy the same environment. Until now deployment-success = staging matched whichever one reported most recently, whoever that was.

Both deployment-success and deployment-failure now take the same @<github-app-slug>/<environment> form the check-* attributes already accept, so you can pin a condition to the deployer: deployment-success = @netlify/staging matches the staging deployment Netlify published and nothing else. The bare form keeps matching a deployment from any source, so existing configurations do not change.

Mergify’s own merge protections gate uses the qualified form too when the reporting method is deployments, so it can no longer be satisfied by a deployment status someone else posted.