Whether the call changed anything.
What is applied: gain the gain only, peak peak limiting only, gain_and_peak both, none nothing.
Where the gain applied during playback comes from: none applies no gain, track and album use the respective stored value, auto follows the playback order (track gain in shuffle, album gain otherwise).
Always true here; a failed call resolves with ApiFailure instead.
Successful response from
replaygain.setMode.