message: Document change
diff: @@ -25,6 +25,7 @@ pub struct FullTrack {
  pub external_ids: HashMap<String, String>,
  pub external_urls: HashMap<String, String>,
  pub href: Option<String>,
  + /// Note that a track may not have an ID/URI if it's local
  pub id: Option<TrackId>,
  pub is_local: bool,
  #[serde(skip_serializing_if = "Option::is_none")]
  