vendor=default in say.synthesizer should be taken to mean use default vendor PLUS label, if a label was set in default app speech settings

[davehorton]

Given this application default configuration

     "defaults": {
        "synthesizer": {
          "vendor": "deepgram",
          "label": "dodo",
          "language": "en-US",
          "voice": "aura-asteria-en"
        },
        "recognizer": {
          "vendor": "deepgram",
          "label": "dodo",
          "language": "en"
        }
      }

and this application

      {
        "verb": "say",
        "text": "<speak>\n<prosody volume=\"loud\">Hi there,</prosody> and welcome to jambones! \njambones is the <sub alias=\"seapass\">CPaaS</sub> designed with the needs\nof communication service providers in mind.\nThis is an example of simple text-to-speech, but there is so much more you can do.\nTry us out!\n</speak>",
        "synthesizer": {
          "vendor": "default",
          "language": "en-US"
        }
      }

The feature server will currently attempt to use for TTS {vendor=deepgram, label=null}.

Instead, when say.synthesizer.vendor=default, and no say.synthesizer.label is set, it should use the default TTS vendor and whatever label, if any, is set at the default