Closes#32. Enable Users / Deployments to change the host where
OpenAI API calls are directed to. This enables project like
[Helicone](https://www.helicone.ai/) (Observability of LLM ops)
for tracking prompt/responses quality in real-time.
Configuration:
- User: App > Settings > Advanced > API host (e.g. "oai.hconeai.com")
- Deployment: set the 'API_API_HOST=...' environment variable
User takes precedence over deployment over api.openai.com. Realtime
switching in chat apps works well.
Note: the Helicone team is fixing dashboard reporting for 'streaming'
over the /v1/chat/completions endpoint.
Enrico Ros