Nothing is built-in to automatically pose as certain users as far as I know. However, there are probably lots of ways to do this depending on how your app is designed.
I’m no expert but I’ve been using a type of role based access control for my apps. The app changes its content and functionality based on the role rather than the user. This way, if I want to “be” a certain user, I simply take their role and re-login.
It’s a deep topic but I read these docs to get me started when designing my app:
I hope this helps and good luck.