Consider implementing a proxy to support any future tool_calls responses

[fjsj]

To support Function calling, i.e, tool_calls responses on any OpenAI endpoints, perhaps the easiest way is to implement a proxy to OpenAI's API. That means we simply route calls to it, and process responses. We need to have a allowlist of paths, though, to avoid regular users to call sensitive OpenAI API endpoints.

[fjsj]

Dropped because we want some custom API as similar tools do: #13