fix: kf_authentication.py fails for some urls

[ca-scribner]

The previous iteration worked if the url passed to kubeflow_login was the kubeflow host domain (eg: http://my.kubeflow/), but not if the url was any other valid url under the domain (eg: http://my.kubeflow/pipelines). This was because some of the request.gets in the authentication flow needed the domain rather than the target url. This was missed because only the domain was tested when this was first written.

These updates fix this problem - the authentication now works for all valid urls in the domain. Note that authentication will not work for any page that does not exist (eg: http://my.kubeflow/somethingThatDoesNotExist will not result in authentication)

[DnPlas]

Hi @ca-scribner and @beliaev-maksim I see some recent conversations, but the PR has been opened for a while. Is this still a relevant change that we want to merge? It seems like this contribution is changing a test file that is not in use. Please close the PR if the changes do not apply/are relevant anymore, or merge it otherwise.

[beliaev-maksim]

Actually, it will be interesting to test authentication via API

Not sure that PR with current state will work on 1.7,need to retest

[ca-scribner]

I bet this needs refactoring to be relevant, but that it will actually be useful in the next few weeks as our bundle tests come back online