Some fields were wrongly parsed as `SpotifyId`s, although they do not
always encode exactly 16 bytes in practice. Also, some optional fields
caused `[]` to be parsed as `SpotifyId`, which obviously failed as well.
- Don't load explicit tracks when the client setting forbids them
- When a client switches explicit filtering on *while* playing
an explicit track, immediately skip to the next track
* Expose all fields of recent protobufs
* Add support for user-scoped playlists, user root playlists and
playlist annotations
* Convert messages with the Rust type system
* Attempt to adhere to embargos (tracks and episodes scheduled for
future release)
* Return `Result`s with meaningful errors instead of panicking on
`unwrap`s
* Add foundation for future playlist editing
* Up version in connection handshake to get all version-gated features
