Added Roles to Node with MongoDB
The Node app was broken again. Turns out I was a little overeager in changing
functions to arrow functions. It messed up with this in model methods.
I also reworked the claims in the JWT. I replaced _id with the registered
claim sub. I also added roles to the User model, similar to those in
Spring Security, and a I added a private claim admin in the JWT to tell if
the user has admin privileges.