Thanks to @oradsa for this release!
Support Spotify Connect devices, such as Sonos or other smart wifi speakers, which are only visible in the home wifi network and are not shown the the devices list.
This change allows the user to pre-configure a "known devices" with their ids, so playback to those devices will be possible.
It also allows to define an entity id (HA media player entity) that corresponds with the smart speaker, in order to allow controlling the volume and play/pause/next/previous controls that are not allowed when playing though Spotify on such devices via the regular Spotify integration.