What's Changed
* Update unit tests to catch up with langchain-core by eyurtsev in https://github.com/langchain-ai/langserve/pull/743
* upgrade to pydantic 2 by eyurtsev in https://github.com/langchain-ai/langserve/pull/744
* migrate examples to pydantic 2 by eyurtsev in https://github.com/langchain-ai/langserve/pull/745
* chat-playground: update to handle oneOf (resulted from pydantic upgrade) by eyurtsev in https://github.com/langchain-ai/langserve/pull/746
* update default playground to handle oneOf type by eyurtsev in https://github.com/langchain-ai/langserve/pull/747