Proposal: Allow saving and reusing bearer tokens via the auth command

Expected Behaviour

I would like to authenticate the CLI using a token and persist this to the configuration

faas-cli login -g http://example.com --token abc123

And then subsequent CLI commands will reuse this token without needing to specify it via a flag, these two commands would be equivalent after authentication

faas-cli deploy -g http://example.com  --token abc123 --name echo --image theaxer/pycho --fprocess="python index.py"
faas-cli deploy -g http://example.com --name echo --image theaxer/pycho --fprocess="python index.py"

Current Behaviour

faas-cli login only supports basic auth

Context

This is useful when using an authentication proxy in the load balancer layer versus enabling auth directly in openfaas. For example, nginx can make a side request to authenticate a request. We often enable this as a centralized auth layer instead of enabling authentication in each application that is deployed.

Start by reading the faas-cli login and deploy command entry points and how they currently receive authentication flags. Define how a token passed to login is persisted and reused by later commands, then verify that the shown authenticated and tokenless deploy commands behave equivalently.