Function parse_string_enum_set_selection 

pub fn parse_string_enum_set_selection<T>(
    value: &str,
    key: &str,
    item_name: &str,
    parse: impl Fn(&str) -> Option<T>,
) -> Result<Vec<T>>
where
    T: Copy + Eq,

Parses a string enum set from a JSON array of strings.

Product crates still own the concrete enum, canonical names, allowed values, and default set. Forge only handles the shared storage shape and duplicate detection so every service reports consistent malformed enum-set config.