[Feature Existing Product API] Upload Transcription to Conversation API

[i-am-rad]

🌟 Describe the Feature

We currently can: Get / Download transcriptions generated by twilio.

We want support for custom providers to upload transcriptions to conversations so we can use those native features. We also want support for those retrieval APIs so people can download those transcriptions later.

🚀 Justification

Why would this be useful for other developers?

3rd Party support for transcriptions and also adding transcriptions for off platform. So if I build an integration with another dialer platform that handles their own transcriptions I want to be able to add that call log and the externally created transcription.

📝 Suggestions

1. Create a new conversation provider channel type: "Transcription" - This can be used for 3rd parties who only want to provide a transcription or AI analysis tool.

2. Update Add Inbound Message / External Outbound Call

type: SMS, Call, Transcription
-support for SMS so that providers with voice messages can add those transcriptions without needing to build another provider

transcription: "string"
conversationProviderId - supported so we know which provider added it

🧠 Additional Context

Any other details you’d like to share?
None