Integration with Keystone auth

[vexxhost]

Integration with Keystone auth

[okozachenko1203]

@heytrav current version only supports application credential to auth cluster-api against openstack.

[okozachenko1203]

@mnaser Do we have any plan of supporting user/pwd auth method for old versions?

We need to indicate the compatible min openstack version in the doc at least for now (for app credential api, keystone>=13.0.0 Queens)

[mnaser]

@heytrav: I'm not sure about how we can support this without application credentials. we'd have to switch to using trusts instead, I'm not a fan of them...

since application credentials have been around for quite sometime, I think adding support for trusts would be more of a "contributions welcome" sort of change.

[heytrav]

@mnaser @okozachenko1203 Thank you both for your input. We're looking to move to ClusterAPI so we'll explore ways we can integrate additional auth methods.