Support for supplying credentials with clouds.yaml

[pnordh]

clouds.yaml seems to be usual way of supplying credentials these days to all kinds of different openstack utilities and is also recommended by gophercloud via their github.com/gophercloud/utils/openstack/clientconfig package.

By using the github.com/gophercloud/utils/openstack/clientconfig package we would also get support for multiple authentication types, e.g application credentials etc.

[pnordh]

Happy to do this but my initial thought is to replace the current ini configuration file with clouds.yaml + eventual fallback to environment variables (as today).

That would obviously be a backwards incompatible change so would like an ack that you agree before starting.