Function paginate_cursor 

pub fn paginate_cursor<'a, T, F>(
    items: &'a [T],
    cursor: Option<&str>,
    limit: usize,
    key: F,
) -> (Vec<&'a T>, Option<String>)
where
    F: Fn(&T) -> &str,

Cursor-based pagination for list endpoints.

Finds the cursor in items (by comparing key(item) to cursor), skips it, takes limit items, and returns (page, next_cursor). If cursor is None, starts from the beginning.