Separate bluetooth media volume from media

[BurnyBoi]

Currently bluetooth media volume shares the same lock slider as media. Requesting it is separated into its own slider.

[theRoboxx]

I'm also a big fan of this feature request.
But I'm not sure, if a app is able to set the bluetooth media volume with a separate slider.
I looked in the dev documentation and couldn't find a STREAM_BLUETOOTH or something like it to get the bluetooth media volume.
Please correct me, if I'm wrong but every other setting does use a STREAM_*****. See here.