[Feature request] Support multiple versions of vikunja

[Heiss]

Because vikunja changes the api without any notifications, the plugin should think about to support multiple versions... As long as vikunja is in fast development, this could be benefecial. But is also a high maintenance feature, because the sdk needs to be generated for every version and there should be a testing environemtn for this...

Currently i am not so happy to implement this, so there is no need currently.