- Use a builder to not handle multiple optional things and hide the
  multiple server definitions
- Rename types to have shorter names
- Remove unused error types
- Use references and small strings to avoid allocations as much as
  possible
- Set DBus names manually for signals/properties/methods

We do that to check if the outputs of the following commands are
sensible / somewhat compatible:
- busctl --user introspect org.mpris.MediaPlayer2.vlc /org/mpris/MediaPlayer2
- busctl --user introspect org.mpris.MediaPlayer2.mpris /org/mpris/MediaPlayer2

AMADEUS: Simplify the client, the worker will only poll notifications + fixed bug where a notification was returned only after the next arrive

AMADEUS: Continue to implement amadeus, only do basic things for now like update the state and basic logics