Function child_name 

pub fn child_name(parts: &[&str], sep: &str) -> String

Builds a deterministic, DNS-label-safe name for a child resource.

Joins the parts with the separator, appends a deterministic 5-character hash suffix for uniqueness, and truncates the prefix so the result is at most 63 characters. The hash is always appended, even for short names, so names are visually consistent regardless of length.