Function nid_to_long_name 

pub fn nid_to_long_name(nid: i32) -> Option<&'static CStr>

Look up the long name for a NID (e.g. 13 → "commonName").

Returns None if the NID is not in OpenSSL’s object table.

The returned string points to OpenSSL’s static object table; its lifetime is 'static and no allocation is performed.