如何开发可用于多个项目的身份验证/授权插件

I am a newbie for RoR but I liked it so far. For the current project I already developed an authenticaion page where the user will be authenticated before and after login. I know that I will be doing more projects on RoR in the coming weeks as well and I don't want to copy paste my codes to enable authentication in my projects. How can I create an authentication system where I can use it in multiple projects. Are there any plugins already been developed?I am a newbie for RoR but I liked it so far. Fo