Adding LangServe management

[kreneskyp]

Description

This PR adds models, API, and UX for importing and using remoteLangServe instances in IX workflows. LangServe instances are chains that run inside a FastAPI app. This is the start of integration with them.

Future PRs will enable LangServers as chains, tools, and agents.

Steps to use

1. Open LangServers menu
2. Click Add LangServe
3. Enter URL, LangServer schema is automatically imported
4. Modify name and description if needed
5. Click Save

Example

LangServe.and.Tool.mp4

Changes

How Tested

new unittests

TODOs

• Langserve does not yet support Pydantic 2.0

  • Upstream ticket: WIP Pydantic v2 compatibility langchain-ai/langserve#10
  • This PR isn't using LangServe RemoteRunnable yet but it's the ideal way to call the LangServes.
  • A possible alternative is just using httpx directly since the API call is simple.

• Finish testing on LangServerTool and LangServerChain. Responses work but there's a thread safety error raised by asyncio cleanup.

  • Possible this is related to how asyncio is integrated with celery. Hoping that replacing celery with faststream and solves this as it has better asyncio support.

[kreneskyp]

So I finished this a while ago and it was waiting on LangServe to support pydantic2.0. I'm unsure I can actually merge this because of non FOSS license on LangServe. Will explore whether this is possible later since LangServe hosts are limited so far.

The actual usage of LangServe library are minimal, limited mostly to initializing the client chain. This can be done with httpx directly so that might be the best path forward