feat: workload identity federation support (#698)
Using workload identity federation, applications can access Google Cloud resources from Amazon Web Services (AWS), Microsoft Azure or any identity provider that supports OpenID Connect (OIDC). Workload identity federation is recommended for non-Google Cloud environments as it avoids the need to download, manage and store service account private keys locally.
This includes a rollforward of the [previous reverted PR](https://github.com/googleapis/google-auth-library-python/pull/686) and the [fix](https://github.com/googleapis/google-auth-library-python/pull/686) to not pass scopes to user credentials from `google.auth.default()`.
diff --git a/docs/reference/google.oauth2.utils.rst b/docs/reference/google.oauth2.utils.rst
new file mode 100644
index 0000000..5b039ea
--- /dev/null
+++ b/docs/reference/google.oauth2.utils.rst
@@ -0,0 +1,7 @@
+google.oauth2.utils module
+==========================
+
+.. automodule:: google.oauth2.utils
+ :members:
+ :inherited-members:
+ :show-inheritance: