3rd party provider <--- OAuth token ---> Loopback app <--- LB Token ---> Client

app.serializeUser = function(userDataToSerialize, done) {
    app.models.Client.create({
        email: 'foo@foo.com',
        password: 'bar'
  },
  function(err, user) {
    if (err) return done(err);

    app.models.Client.generateVerificationToken(user, function(err, token) {
      if(err) return done(err);

      done(null, {
        userId: user.id,
        accessToken: token
      });
    });
  };