While working on the DB optimisation I discovered one query which does
not follow the 'FieldQuery' interface - 'PlaylistQuery', so I looked
into it in more detail.
One special thing about it is that it uses 'IN' SQL operator, so
I defined 'InQuery' query class to have this logic outside of the
playlist context.
Otherwise, it seems like 'PlaylistQuery' is a field query, even if it
has a very special way of resolving values it wants to query. In the
future, we may want to consider moving this kind of custom
_initialisation_ logic away from '__init__' methods to
factory/@classmethod: this should make it more clear that the purpose of
such logic is to resolve the data that is required to define
a particular FieldQuery class fully.
Allow generating extm3u playlists so that they contain additional item fields such as the `id`.
The feature is required by the mgoltzsche/beets-webm3u plugin (M3U server) to transform playlists using a request based item URI template which may require additional fields such as the `id`, e.g. `beets:library:track;$id`.
Sometimes, there are other playlists that are created (e.g., Top Missed Recordings of 2023, Top Discoveries of 2023). Right now, I am excluding these. We may want to address them separately.
Do not let the web plugin overwrite the Content-Length header with the full file length since flask/werkzeug sets the requested range's/chunk's size when handling a range request.
This allows to play large audio/opus files using e.g. a browser/firefox or gstreamer/mopidy without making a reverse-proxy/nginx emulate range request support and hide range-related headers from the backend.
