feat: workload identity federation support (#686)

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.
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: