New API: Enterprise installation lookup

[moraesc]

We're filling an API gap for GitHub App developers based on community feedback.

Enterprise Installation API

We've added a new API that lets a GitHub App find out if it's installed on an enterprise and what its installation ID is. This matches the existing APIs that do the same for organizations, repositories, and users. These APIs help apps get an installation token for an enterprise faster, rather than paginating through a list of all installations to find the right target.

Thank you to the broader GitHub Actions community and Enterprise Apps preview participants for calling out this gap so that we could solve it.

See the corresponding changelog here: https://github.blog/changelog/2026-05-13-new-enterprise-installation-api-now-in-public-preview