GitHub App Installation Authentication

[jmeridth]

Currently the GitHub OSPO GitHub Actions only allow authentication via a personal access token (PAT). Many enterprise customers require GitHub App authentication for their organizations. This is to ensure authentication is not related to a single user.

We should extend each GitHub Action to allow for this.

This introduces 3 new environment variables:

• GITHUB_APP_ID
• GITHUB_APP_INSTALLATION_ID
• GITHUB_APP_PRIVATE_KEY

See documentation for more details.

Repos (PRs):

• [x] stale-repos: https://github.com/github/stale-repos/pull/92
• [x] cleanowners: https://github.com/github/cleanowners/pull/30
• [x] issue-metrics: https://github.com/github/issue-metrics/pull/221
• [x] evergreen: https://github.com/github/evergreen/pull/79
• [x] contributors: https://github.com/github/contributors/pull/80
• [x] automatic-contrib-prs: https://github.com/github/automatic-contrib-prs/pull/43

[jmeridth]

Complete