Accept `model` parameter in `create_transcription`

[themire]

https://learn.microsoft.com/en-us/azure/ai-services/speech-service/batch-transcription-create?pivots=rest-api#request-configuration-options

You can set the model property to use a specific base model or custom speech model. If you don't specify the model, the default base model for the locale is used. For more information, see Use a custom model and Use a Whisper model.