Function parse_enum 

fn parse_enum<T: DeserializeOwned>(value: Option<&Value>) -> Option<T>

Deserialize a wire-string enum variant from an optional JSON value. Returns None for missing field, wrong JSON type, or unrecognised variant - the three failure modes share a single drop path. Each enum carries #[serde(rename_all = "snake_case")] so this is just the typed wrapper.