Support CA certificates in CLI

[vidok]

Problem Description

The ./bin/connectors login does not support passing in SSL parameters to specify the CA cert. It's unclear what users need to do in order to connect with a HTTPS enabled Elasticsearch cluster. If the answer is for users to use -c to pass in their own config.yml file with the Elasticsearch connection settings (along with the SSL ones), it will be helpful to clarify in the docs.

Proposed Solution

Customers can pass --cert-path when authenticating the cli. Or configure the certificate path manually in the config.yml.