Hi next community, I am looking for some advice for figuring out my project. I am currently developing a live doc web app and currently planning out how to do authentication. I am struggling on how I need to set it up so that I can make sure user info is stored to the data base so then later on it can be tied to docs made. My current plan is to use AuthJS( formally NextAuth) and the tech stack I am using is a NextJS frontend, NestJS backend, and a firestore database. Getting into even more details the part I am struggling on understanding is how I can send the info I need to the backend as well as making sure I can verify that the info sent is someone in the database or a username isn't taken up. There are a lot more questions I am trying to figure out with this but will try to limit it to this for now. If there is any clarification needed please let me know.