def initialize(options = {})
            @api_key = options[:api_key] || ENV['MAILCHIMP_API_KEY']
            @list_id = options[:list_id] || ENV['MAILCHIMP_LIST_ID']
            Rails.logger.info("MailchimpService::Client.initialize: #{@api_key}, #{list_id}")
            @gibbon = Gibbon::Request.new(api_key: api_key, debug: true)