feat: address legacy requests

Author: matsk-sinch

sinch/domains/numbers/models/available/activate_number_request.py

@@ -29,7 +29,8 @@ def __init__(self, **data):
 
         for key in ("voiceConfiguration", "voice_configuration"):
             if key in data and data[key] is not None:
-                voice_type = data[key].get("type")
+                # Address legacy requests
+                voice_type = data[key].get("type") or "RTC"
                 voice_config_class = voice_config_map.get(voice_type, VoiceConfigurationCustom)
                 voice_config_class(**data[key])