Function rest_base_url 

pub(crate) fn rest_base_url() -> String

Base URL of the muxbus REST API.

The env override exists for tests and for running against a local muxbus server (http://localhost:3100, registered in the dev Cognito app client). Previously private to pkce.rs; promoted here because tier 4 needs the same resolution and two copies of “where is the cloud” is exactly the drift this report set out to remove.