verify the user's identity server side

[elmariachi111]

currently the whole login process runs client side. On the server side can only verify that the JWT token provided is a valid JWT token but we cannot verify (yet) that the signature is valid. Use Auth0 private keys to validate the JWT and its user on the backend. Feel inspired by https://github.com/embiem/WirVsVirus/blob/develop/backend/wirvsvirus/auth.py