Function resolve_prefixed_var 

pub fn resolve_prefixed_var(prefix: &str, suffix: &str) -> String

Resolves {prefix}_{suffix}, falling back to unprefixed MICROMEGAS_{suffix} when the prefixed name is unset, or always when prefix is empty.

suffix is passed without the MICROMEGAS_ prefix (e.g. "OIDC_CONFIG", "DEFAULT_AUDIENCE").