CDNI Cache Control Metadata

This specification adds new Cache Control objects that complement the basic Cache Control Metadata object defined in RFC8006, providing content providers and upstream Content Delivery Networks (uCDNs) more fine-grained control over downstream CDN (dCDN) caching. Use cases include overriding or adjusting cache control headers from the Content Service Provider (CSP) source or origin, bypassing caching altogether, or altering cache keys with dynamically generated values.