AudioSendModeRequest is not exposed to the API

[cyb3rdog]

Issue description

There is this AudioSendModeRequest method allowing to set the AudioProcessingMode to other value than the default value
of AudioProcessingMode_AUDIO_UNKNOWN.

Unfortunatelly, it seems that there is no exposed RPC call to invoke that request from API to set up the AudioProcessingMode in vic-gateway to other value than this initial value, and therefore the only sound currently received from the AudioFeed is constant test tone...

Suggested Resolution

• to expose this call as rpc to enable the actual audio to be streamed through AudioFeed.

Goal

• to use this for what it was originally intended - to set it up for example to AUDIO_VOICE_DETECT_MODE, and process the audio with custom voice recognition systems even externally with the API, for all robots out there.