pub fn validate_city(city: &str) -> Result<(), ProxyError>Expand description
Returns Ok(()) when city is a valid operator-supplied city
label, otherwise an crate::error::ProxyError::InvalidGeoMetadata.
city must be 1-100 characters (UTF-8 byte length). The format is
operator-defined; common conventions include "San Francisco",
"São Paulo", "Saint-Étienne".