Add new token endpoint

[GalMunGral]

Closes #1246

How to test:

1. Change app/config.py:

- auth_redirect_uri = f"{API_HOST}{API_V2_STR}/auth"
+ auth_redirect_uri = f"{API_HOST}{API_V2_STR}/auth/token"

2. In Keycloak admin console, under the client "Access settings", change "Valid redirect URIs" to "http://localhost:8000/api/v2/auth/token"
3. Click "log in" on the frontend. You should see the JSON returned by this endpoint, which includes access and refresh tokens. This is just to trigger a call to the endpoint with a valid authorization code. In a real scenario, we'd configure Keycloak to redirect to another app (e.g. IDOT TREC) with the auth code, which would in turn call this endpoint with the same auth code.

[longshuicy]

Code looks good and everything works for me.

If you'd like to test, instead of hard coding the auth_redirect_uri to /token, alternatively you can set this as an env in pycharm. (But you still have to add this to the allowed redirect url in keycloak)