Support interactive authentication for API key used in previous session #70
Description
sfcc-ci auth:login should support authentication flow for interactive user authentication (via Oauth implicit flow) and honour API key of the previous session. The CLI currently memorizes the API key already in the local client configuration.
Running the command sfcc-ci auth:login may read the memorized API key and start the Oauth flow to authenticate the user interactively. This allows users who frequently authenticate via the same API key to re-authenticate without explicitly type the API key as a parameter of sfcc-ci auth:login $API_KEY