Duenna will be a drop-in User Management System for open source / open knowledge websites. A separate version will be available for commercial sites with additional functions.
Duenna will deal with your needs for user authentication, and provide you with secured hooks which you need to integrate that with user authorisation.
Duenna is a library solution; you make use of as many - or as few - modules as you require, and can upgrade or downgrade it whenever you need to.
Duenna offers a secured token-based option based around a single identity concept.
Duenna will make you life easier, and your project development faster. And who can complain at that?