User authentication-jwt with MySQL

@cioddi y travaille déjà.

Depuis le 29/10/2020.

## Steps to reproduce

Follow the authentication tutorial below:
https://loopback.io/doc/en/lb4/Authentication-tutorial.html

## Current Behavior

The authentication-jwt package includes the User model but it's using a strict mode "false" and has, for example, an id type string which is not usual with MySQL.
It also doesn't create automatically the table in database when using npm migrate

## Expected Behavior

It should create automatically the table user in db and be compatible with MySQL schema.