Roon API volume change of grouped zone

[DrCWO (C.W. Oehlrich)]

@Joost_de_Bonth

separate change_volume commands are run for each output

I also tested this for rooDial rooDial a Wireless Volume Knob for Roon with Microsoft Surface Dial - Audio Products - Roon Labs Community

I found no way except changing each output of the zone separately.