Add in custom cookie attributes

[whiteh]

Add in capability to set custom cookie attributes.

cookieAttributes - Set on the Netacea session cookie
captchaCookieAttributes - Set on the Netacea captcha cookie

Usage

netacea = (require 'lua_resty_netacea'):new({
   ...
   cookieAttributes              = 'Path=/; httponly;',
   captchaCookieAttributes = 'Path=/; httponly;',

Outcome (in a HTTP response)

Set-Cookie: _mitata=aaa....;Path=/; httponly;
Set-Cookie: _captchamitata=aaa...;Path=/; httponly;