support custom tts streaming (#1023)

* support custom tts streaming

* wip

* wip

* wip

* wip

* wip

* wip

* fix review comments

lib/utils/tts-streaming-buffer.js

@@ -214,7 +214,7 @@ class TtsStreamingBuffer extends Emitter {
   }
 
   async _api(ep, args) {
-    const apiCmd = `uuid_${this.vendor}_tts_streaming`;
+    const apiCmd = `uuid_${this.vendor.startsWith('custom:') ? 'custom' : this.vendor}_tts_streaming`;
     const res = await ep.api(apiCmd, `^^|${args.join('|')}`);
     if (!res.body?.startsWith('+OK')) {
       this.logger.info({args}, `Error calling ${apiCmd}: ${res.body}`);
@@ -277,7 +277,8 @@ class TtsStreamingBuffer extends Emitter {
       // DH: add other vendors here as modules are added
       'deepgram',
       'cartesia',
-      'elevenlabs'
+      'elevenlabs',
+      'custom'
     ].forEach((vendor) => {
       const eventClassName = `${vendor.charAt(0).toUpperCase() + vendor.slice(1)}TtsStreamingEvents`;
       const eventClass = require('../utils/constants')[eventClassName];