Allow users to configure `base_url` per provider to connect to
compatible third-party endpoints (Azure OpenAI, Ollama, vLLM, one-api,
etc.). All four API providers (Anthropic, OpenAI, Gemini, MiniMax) now
accept an optional `base_url` in config which is passed through to
their respective SDKs.
Co-authored-by: Cursor <cursoragent@cursor.com>
ChrisPan