pub fn resolve_api_key(
default_env: &str,
override_env: Option<&str>,
) -> Option<String>Expand description
Resolve an API key from the environment.
default_env is the env var the built-in registry expects (e.g.
"GROQ_API_KEY"). override_env is an optional per-provider
override from config.toml’s [providers.<name>] api_key_env = ....
When set, it takes precedence — a user who’s already standardized on
LLM_API_KEY for everything can point all their providers at it.
Empty values are treated as unset (matches the existing
get_cloud_api_key semantics).