Function forward_openai 

pub async fn forward_openai(
    client: &Client,
    base: &str,
    headers: &HeaderMap,
    body: Bytes,
) -> Result<(StatusCode, HeaderMap, Bytes), ProxyError>

Forward one POST /v1/chat/completions request and return its response buffered. Observe-mode passthrough for the OpenAI-compatible inbound endpoint — byte-identical relay.

Errors

Returns ProxyError::Upstream on a transport-level failure.