Enable non-root user access

[harryhaaren]

Ensure that a good UX is provided for users who are not running as root. This probably involves writing udev rules to enable non-root user access to the USB devices that are supported by ctlra.

[harryhaaren]

Thanks Robin for mentioning Ardour's udev rule for the machine2:
https://github.com/Ardour/ardour/blob/850b0d3e0940df07edaafed30e6517ec3f6f309c/tools/udev/99-maschine2.rules

[Be-ing]

Mixxx uses a udev rule that whitelists known USB vendor IDs. I think this is a better approach than whitelisting combinations of vendor and product IDs because then everyone implementing support for a new controller would have to make a new udev rule for it. However, there are only a few companies making HID controllers that people would be interested in using with Ctrla, so whitelisting a few vendors should make it so few people have to care about this issue.

It will be important for a good user experience to communicate to packagers that the udev rule needs to be installed in the appropriate place for the distribution.

[harryhaaren]

Ah thanks for the input here - Udev rules it is, Thanks for the note to investigate the existing rules that Mixxx puts in place for USBHID controller devices .

[Be-ing]

Ableton's USB vendor ID is apparently 2982.