Function parse_add_entry 

fn parse_add_entry(entry: &str) -> Result<(String, String), String>

Splits an add entry of the form "Name: value" into (name, value).

Mirrors APISIX’s ^([^:\s]+)\s*:\s*([^:]+)$: the name has no colon or whitespace, and the value part must be non-empty and colon-free.