Before we can call a Google Cloud API, we have to obtain an OAuth access token. We can obtain access tokens for a user (by following the OAuth authorize flow) or for a service account, and most APIs will happily accept both kinds of tokens. But there are some APIs that won’t accept access tokens issued to service accounts. Examples for such APIs include the Cloud Identity API, parts of the Directory API, and several non-Cloud APIs. If we want to use these APIs in an unattended scenario, we ...
