def connection
      @connection ||= Faraday.new(conn_opts) do |http|
        http.url_prefix = endpoint
        if @access_token
          http.authorization :Bearer, @access_token
        end
      end
    end
def connection
      @connection ||= Faraday.new(conn_opts) do |http|
        http.url_prefix = endpoint
        if @access_token
          http.authorization :Bearer, @access_token
        end
      end
    end
HTTP connection for the Particle API

 @return [Faraday::Connection]