FeathersJS + Auth0: Authenticated but user not populated - authentication

Question

I installed the Auth0 lock and can login on my client side, with an idToken in my localStorage.
I send this idToken to my API server - a FeathersJS server, which is basically an extension to an Express server. I get authenticated correctly using JWT, but the user is empty in my req object (it's called student here):
{ authenticated: true,
query: {},
provider: 'rest',
headers: { (truncated...) },
student: {},
payload:
{ iss: 'https://mydomain.eu.auth0.com/',
sub: 'myusername',
aud: 'myaudience',
exp: 1494125072,
iat: 1494089072 } }
The 5 last lines are the payload contained inside Auth0's idToken.
The fact that my student user object is empty is kind of normal when I think about it, because the app doesn't know how to link a Auth0 user to one of my database users. It's done by the username property. But how do I tell my Feathers app that? Is there a populateUser or something similar?
I remembered such a function in the old Feathers, but the new one uses the common hook's populate function: see here:
populateUser -> use new populate hook in feathers-hooks-common
So I tried this new populate hook, but unfortunately it's only an After hook, which doesn't make sense since I want to populate the user before making the request.
And now I'm stuck. I mean, I could write my own before hook which populates the user, but I bet there's some nicer way to achieve what I want.
Below is some relevant code:
authentication.js
const authentication = require('feathers-authentication');
const jwt = require('feathers-authentication-jwt');
const oauth2 = require('feathers-authentication-oauth2');
const Auth0Strategy = require('passport-auth0').Strategy;
module.exports = function () {
const app = this;
const config = app.get('authentication');
// Set up authentication with the secret
app.configure(authentication(config));
app.configure(jwt());
app.configure(oauth2({
name: 'auth0',
Strategy: Auth0Strategy,
}));
// The `authentication` service is used to create a JWT.
// The before `create` hook registers strategies that can be used
// to create a new valid JWT (e.g. local or oauth2)
app.service('authentication').hooks({
before: {
create: [
authentication.hooks.authenticate(config.strategies)
],
remove: [
authentication.hooks.authenticate('jwt')
]
}
});
};
config file
{
...
"authentication": {
"entity": "student",
"service": "students",
"secret": "SAME_SECRET_AS_BELOW",
"strategies": [
"jwt"
],
"path": "/authentication",
"jwt": {
"header": {
"type": "access"
},
"audience": "SAME_AUDIENCE_AS_BELOW",
"subject": "anonymous",
"issuer": "https://mydomain.eu.auth0.com/",
"algorithm": "HS256",
"expiresIn": "1d"
},
"auth0": {
"clientID": "SAME_AUDIENCE_AS_ABOVE",
"clientSecret": "SAME_SECRET_AS_ABOVE",
"domain": "https://mydomain.eu.auth0.com/"
}
}
}