Allow overriding the base URL for OpenAI in config.toml

What variant of Codex are you using?

CLI

What feature would you like to see?

If I have this in my config:

model_provider = "openai"

[model_providers.openai]
name = "OpenAI"
base_url = "http://localhost:8080/v1"
wire_api = "responses"

Codex doesn't seem to respect it. If I am understanding the code correctly, since it's a built-in provider, we don't take into account any overrides in the TOML.

It would be great if this was supported so I can permanently use codex through a proxy (this is needed for my use case).

(I know I can override it via env vars, but config would be better for my use case)

Additional information

_No response_