[ListenBrainz] Additional Metadata

[MaxEtMoritz]

Listenbrainz accepts additional metadata for listens / now playing notifications. Some fields are standardized, but in theory everything could be submitted.
The currently standardized fields are documented here.

Of those additional metadata fields, the following ones could be interesting to implement, in addition to the already implemented mbid submission:

• duration_ms / duration. The length of the track.
  This one is my top priority, as it also shows up on the LB website front-end if supplied.
• media_player (and media_player_version, if determinable). Information about the player used for listening to the track.
• submission_client / submission_client_version. Information about what program submitted the listens (mpris-scrobbler in this case).

And for scrobbling a browser:

• origin_url. URI of the page the track was listened on.

To clarify, the additional metadata is not only useful for the scrobble, but also for the now_playing (at least the duration of the track. As far as i know, supplying a duration in now_playing causes the now_playing to disappear after the track is finished instead of after a default time of 4 minutes)