Adds support for configuring volume filtering

[jrg1381]

Supports unreleased volume filtering feature:

{
  "transcription_config": {
    "language": "en",
    "audio_filtering_config": {
      "volume_threshold": 4
    }
  }
}

[HennerM]

can't this be a property in the top level dict?

[jrg1381]

Do you mean audio_filtering_config should be a top level property of the whole thing, or that volume_threshold should be a property in transcription_config?

If the first, then I think audio filtering is a transcription option (and unlike a standalone option configuring a speech capability)

If the second, it's because it follows the related openapi-spec MR and audio_filtering_config is open for extension, even though it only has one setting at the moment - the analogy is with ``speaker_diarization_config`.

[jrg1381]

Resolving since the openapi-specifications change is merged.

[philiprbrown]

LGTM