login abstract method
Login the user to this app
Does the login requests. 1. for auth, 2nd to get the keys.
If there are more data in the backend, then it is possible to call it via the jwt what is returned by the done login request.
The other backend can validate the jwt
Implementation
Future<UserLoginOut> login(
{required String baseUrl,
required String authToken,
required String userIdentifier,
required String password,
dynamic hint});