Jellyfin integration

As an alternative/addition to logging in with Plex, integration is planned with Jellyfin open source media server.

Note that Jellyfin and Plex have slightly different features and provide slightly different data. Not all features from Plex will be supported with Jellyfin integration, and vice versa.

There is currently no timeline for when this will be complete. It is in progress and partially working already, but there are a lot of updates required throughout the app to handle the differing capabilities of Jellyfin.