feat(Text to Speech): Revised service to use the default US South URL if none is supplied

Author: mediumTaj

Scripts/Services/TextToSpeech/v1/TextToSpeech.cs

@@ -146,6 +146,11 @@ public TextToSpeech(Credentials credentials)
             if (credentials.HasCredentials() || credentials.HasWatsonAuthenticationToken() || credentials.HasIamTokenData())
             {
                 Credentials = credentials;
+
+                if (string.IsNullOrEmpty(credentials.Url))
+                {
+                    credentials.Url = Url;
+                }
             }
             else
             {