We currently don't save the installation ID for GH Apps after they are installed, likely because it isn't necessary for repo syncing to function. However, we do require the installation ID to use GH Apps with Batch Changes, because we need the installation ID to generate an installation access token to authenticate the client with.

We should verify with the GH App team that we're not missing it somewhere or that it's not intentionally left out for some reason. Assuming that's not the case, we should add it the github_apps table and include it when writing new records. We should also verify with the GH App team whether or not we need to backfill installation IDs for existing records.