Function expand_name 

pub fn expand_name(
    source: &str,
    node_name: &str,
    namespace: &str,
) -> Result<ResolvedName, ()>

Expand a source-level ROS name to its fully-qualified form (ROS 2 name expansion rules):

• /absolute/name → unchanged.
• ~ / ~/rest (private) → /<ns>/<node> / /<ns>/<node>/rest (ns == "/" collapses: /<node>/rest).
• relative/name → /<ns>/relative/name (ns == "/" collapses: /relative/name).

namespace may be given with or without a leading /; empty means root. Errors on: empty source, a private name with an empty node_name, or a result exceeding MAX_RESOLVED_NAME_LEN.