I need a backend web dev. JS, NodeJS, mongoose.

Hello there!

I'm currently working on a website with a friend of mine and we're stuck configuring user authentication and protected routes.
It's a website related to Workouts/Exercises. We have 3 models and we're creating relationships between them, we're almost at the end but would like to be sure that the password encryption and decryption using bcrypt works 100% but we're struggling. Could you help me? Maybe have a look at the code and see what's missing. We're working with JavaScript and Mongo DB Compass.

Basically the assistance needed is related to:
- register a user and sign in
- after signing in, maintaining the session active until the user logs out
- be able to save exercises in the active user's profile so that the next time the user signs in the exercises are there saved in the account

P.S: most of the code is done and relationships between models are created and working. Help is mostly needed in the authentication/authorisation/protected routes part.

Thank you in advance