[SDK-2318] feat: Store changes made to the user object during the onLogin event hook

[evansims]

Ensure changes made to the user object during the onLogin event hook are stored and propagated for later use, as suggested here.

[JoeyHoutenbos]

@frederikprijck with this change the onLogin callback now has to return an array instead of Auth0\Login\Auth0User object.
But an array obviously doesn't implement the Illuminate\Contracts\Auth\Authenticatable class which is required for the Auth::login(...) call here: https://github.com/auth0/laravel-auth0/blob/master/src/controllers/Auth0Controller.php#L51

So I don't get how this is supposed to work. Could you please help me out?