Support App ID for status source

## Prerequisites:

* Is the functionality available in the GitHub UI? If so, please provide a link to information about the feature.
Yes
not super clear in the docs, but available in UI

* Is the functionality available through the GitHub API? If the functionality is available, please provide links to the
API documentation (https://developer.github.com/v3/) as well as the Octokit documentation (https://octokit.github.io/).
Yes, search `required_status_checks.checks[].app_id` in https://octokit.github.io/rest.js/v18

## New Feature

Please describe the desired new functionality:
In UI/API, we are able to choose which app is allowed to post certain statuses (or at least, which we accept for required status completion). Can we add this to safe-settings to ensure statuses come from gh actions

Commencez par déterminer comment safe-settings représente et applique les vérifications d’état requises, puis comparez ce flux avec le champ de l’API GitHub required_status_checks.checks[].app_id. Le travail est terminé lorsque la configuration peut limiter les états acceptés à un App ID spécifié et que ce comportement est couvert par des tests.

Rédigé par le modèle d'indexation à partir du texte de l'issue.