Feature Request: Add CosmosDbTranscriptStore

[mdrichardson]

Issue

This is a customer request, spawned from this issue.

I don't see a reason why we couldn't do this, but I definitely wouldn't default to it as Cosmos is likely going to be more expensive to implement this with than Blobs.

Proposed change

Create a CosmosDbTranscriptStore class that implements ITranscriptStore and is part of the Microsoft.Bot.Builder.Azure library (it could maybe live elsewhere; there isn't a great place for it).

Component Impact

Describe which components need to be updated

Customer Impact

Would allow customers to keep all storage providers under Cosmos, if desired. Note, however, that this would likely be more expensive than Blob storage.

Tracking Status

Dotnet SDK TODO

• [ ] PR
• [ ] Merged

Javascript SDK TODO

• [ ] PR
• [ ] Merged

Python SDK TODO

• [ ] PR
• [ ] Merged

Java SDK TODO

• [ ] PR
• [ ] Merged

Samples TODO

• [ ] PR
• [ ] Merged

Docs TODO

• [ ] PR
• [ ] Merged

Tools TODO

• [ ] PR
• [ ] Merged