modules and user management.md

• Modules are for sub-applications, reusable across projects. rights is a fairly good example.
• Modules are not just a way of organizing your code into directories and don’t work well for that purpose.
• User management doesn’t easily fit in a module because it is usually coupled to application business logic.
• For the same reason, user management does not easily abstract into any kind of extension or into the framework APIs.
• So you have to implement user management yourself and the right place is in the main app, just like yii2-app-advanced currently demonstrates.
• The best you can do to abstract parts of the user management functionality into reusable code is to put some of the functionality into extension classes as nineinchnick/yii2-usr does.