何时以及如何使用我的安全模型进行设计？

I'm not sure how to proceed. I have an idea for a web application(s) but I'm not sure which part to do first. If my application has an authorization and authentication need, do I create that first and then the rest of the program or do I do the other (to me more fun) stuff first and then plug in the user authentication later?I'm not sure how to proceed. I have an idea for