Send 400 / 500 error status on Internal Server Error

[ElishaKay]

We've gotta bubble up the error from the server when there is an "internal server error" - probably need a try/catch on the main API Request handler and throw an error on the chat_completion helper function

It's a gorgeous gradient, but the user is left poetically waiting with no indication on a server error

Perhaps in the create_chat_completion function:

https://docs.gptr.dev/docs/gpt-researcher/llms/testing-your-llm

[assafelovic]

@ElishaKay good point, let's do a PR for this?