feat (ui/react): support resuming an ongoing stream

[jeremyphilemon]

Background

This pull request adds the ability for clients to resume an ongoing chat generation stream after a network disconnect.

Summary

This pull request adds support for the useChat hook to resume an ongoing chat generation stream by exposing experimental_resume() that can be called by any client, typically during the initial mount of the hook.

The experimental_resume function makes a GET request to the api endpoint you've initialized the hook with (or /api/chat by default) and streams the contents of the stream if it is active or fails silently if it has ended.

In order for experimental_resume to work as intended, it requires the usage of the resumable-stream package for stream creation and a redis instance for the package to manage the pub/sub mechanism.

Verification

An example has been added at examples/next-openai/app/use-chat-resume to test the feature. Follow the following steps to test it end-to-end:

1. Run the development server
2. Navigate to http://localhost:3000/use-chat-resume
3. Send a message that will have a longer generation duration, example "Write an essay about Michael Jordan"
4. Once the generation starts, click the chat id above to open the conversation in a new tab
5. Verify the stream gets resumed

Tasks

• Tests have been added / updated (for bug fixes / features)
• Documentation has been added / updated (for bug fixes / features)
• A patch changeset for relevant packages has been added
• Formatting issues have been fixed (run pnpm prettier-fix in the project root)

Future Work

Possibly unify resumeChatApi and callChatApi and avoid code duplication.

[lgrammel]

language

[jeremyphilemon]

updated, but can you verify since it was unclear what to improve

[lgrammel]

CC @iteratetograceness for visibility regarding the useChat chat store refactoring.

[jeremyphilemon]

Created a new pull request since the tests here have bugged out #6052