Set test_mode on the client

[mkcode]

Hi, Our team had recently run into an issue where we updated some templates unintentionally in production, while we were developing a new feature locally - in development mode.

Looking over the code, I would expect to be able to configure the client to run in test mode during the initial client setup / configuration and have that apply for all relevant api calls. I would expect this code to live on the configuration object here: https://github.com/HelloFax/hellosign-ruby-sdk/blob/v3/lib/hello_sign/configuration.rb#L60-L75, but I do not see it.

Perhaps there is a technique to fake this sort of test_mode operation by specifying a non verified client id?

Does anyone have a good workaround pattern to set test_mode on a per client basis? If not, would this be a worthwhile feature to add?

I'd really like to be able to do this:

HelloSign.configure do |config|
  config.api_key = ENV['HELLOSIGN_API_KEY']
  config.test_mode = true
end

Thanks!