class Google::Auth::OAuth2::STSClient

def make_request options = {}
  request_body = {
    grant_type: options[:grant_type],
    audience: options[:audience],
    scope: Array(options[:scopes])&.join(" ") || [],
    requested_token_type: options[:requested_token_type],
    subject_token: options[:subject_token],
    subject_token_type: options[:subject_token_type]
  }
  unless options[:additional_options].nil?
    request_body[:options] = CGI.escape MultiJson.dump(options[:additional_options], symbolize_name: true)
  end
  request_body
end