Support App ID for status source

[markjm]

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

[svg153]

Apparently this is working with https://github.com/repository-settings/app (old probot/settings), without specific code for it.

• https://github.com/joke/spock-mockable/blob/main/.github/settings.yml#L42-L49
• chore(deps): bump objenesis from 2.6 to 3.2 joke/spock-mockable#194