The goal is to create an application that integrates with others that require authentication.
It is a sales application, so for example the user would register in my application. Now if they create a contract and want to use docusign (they may or may not, and if they do they have their own docusign account nothing that we provide) - then while inside my application they would click “link your docusign account” which after authentication would be able to use the docusign API.
Or maybe they have a CRM they use and want to sync contacts and then edit them from inside my app etc and that CRM requires authentication and refresh tokens etc.