Add authentification to API
Our bitcart backend API is written in fastapi.
It is located in `main.py` file and` api/` folder.
Currently it is accessible by everyone.
We should add authentification, either Token, or JWT, or some other kind of auth.
Some useful links:
https://fastapi.tiangolo.com/tutorial/security/intro/
https://fastapi.tiangolo.com/tutorial/security/get-current-user/
https://fastapi.tiangolo.com/tutorial/security/first-steps/
https://fastapi.tiangolo.com/tutorial/security/simple-oauth2/

The user model is defined in `schemes.py`(pydantic validation for output in API), and database model in `models.py`.
Also, when user is logged in API should be restricted  to displaying only those wallets, store, products, invoices that user have.
User has is_superuser value, if it is `True`, then all data should be displayed.
If user is not superuser, users list might not be accessible at all, or there should be a new endpoint added:
`/users/current`
Or `/profile`
Returning logged user info.