Address TODO/FIXME items: Retry handling

[cybermaggedon]

Rate-limiting exception handling is incorrect in several LLM providers (OpenAI, Mistral, Cohere, vLLM)

[CuriousHet]

Hi @cybermaggedon

1. should catch 429(TooManyRequests) or 503(Service Unavailable).
2. should i assume modern versions of SDK. if project have older versions, then exception names might be different.

[cybermaggedon]

1. Yes, both those errors, which are retryable. We throw TooManyRequests from exception.py for a 429 error. LlmError for the 503 makes sense. Both those exceptions are in exceptions.py. The pubsub infrastructure we have takes care of the retry mechanism as appropriate for each pubsub system.

2. Yes, we generally want to sit on cutting edge SDK and track the latest because everything is changing rapidly. Feel free to validate against just the latest SDK

Thanks @CuriousHet !

[cybermaggedon]

Would be grateful if you could PR against latest release branch, at the moment that's release/v2.3 @CuriousHet