What is missing?

The websso keystone authentication method is a way to get a token via the websso method in Skyline/Horizon to allow the user to auth to their SSO via a web browser. See a Python implementation at https://github.com/IFCA-Advanced-Computing/keystoneauth-oidc as well as an effort to upstream it at https://review.opendev.org/c/openstack/keystoneauth/+/970328 It's possible to install this plugin via pip today. There's no way to currently create an out of tree plugin for gophercloud which would support this functionality. Related to #3283.