feat: support Azure OpenAI TTS. (#1177)

Author: techotaku

relay/controller/audio.go

@@ -104,10 +104,15 @@ func RelayAudioHelper(c *gin.Context, relayMode int) *relaymodel.ErrorWithStatus
 	}
 
 	fullRequestURL := util.GetFullRequestURL(baseURL, requestURL, channelType)
-	if relayMode == constant.RelayModeAudioTranscription && channelType == common.ChannelTypeAzure {
-		// https://learn.microsoft.com/en-us/azure/ai-services/openai/whisper-quickstart?tabs=command-line#rest-api
+	if channelType == common.ChannelTypeAzure {
 		apiVersion := util.GetAzureAPIVersion(c)
-		fullRequestURL = fmt.Sprintf("%s/openai/deployments/%s/audio/transcriptions?api-version=%s", baseURL, audioModel, apiVersion)
+		if relayMode == constant.RelayModeAudioTranscription {
+			// https://learn.microsoft.com/en-us/azure/ai-services/openai/whisper-quickstart?tabs=command-line#rest-api
+			fullRequestURL = fmt.Sprintf("%s/openai/deployments/%s/audio/transcriptions?api-version=%s", baseURL, audioModel, apiVersion)
+		} else if relayMode == constant.RelayModeAudioSpeech {
+			// https://learn.microsoft.com/en-us/azure/ai-services/openai/text-to-speech-quickstart?tabs=command-line#rest-api
+			fullRequestURL = fmt.Sprintf("%s/openai/deployments/%s/audio/speech?api-version=%s", baseURL, audioModel, apiVersion)
+		}
 	}
 
 	requestBody := &bytes.Buffer{}
@@ -123,7 +128,7 @@ func RelayAudioHelper(c *gin.Context, relayMode int) *relaymodel.ErrorWithStatus
 		return openai.ErrorWrapper(err, "new_request_failed", http.StatusInternalServerError)
 	}
 
-	if relayMode == constant.RelayModeAudioTranscription && channelType == common.ChannelTypeAzure {
+	if (relayMode == constant.RelayModeAudioTranscription || relayMode == constant.RelayModeAudioSpeech) && channelType == common.ChannelTypeAzure {
 		// https://learn.microsoft.com/en-us/azure/ai-services/openai/whisper-quickstart?tabs=command-line#rest-api
 		apiKey := c.Request.Header.Get("Authorization")
 		apiKey = strings.TrimPrefix(apiKey, "Bearer ")