Multi-tenant CDN cache isolation

Design the cache-key normalization and isolation strategy for a multi-tenant CDN to prevent cache poisoning and cross-tenant cache leakage. Threats include: an attacker crafting a request that gets a malicious response cached and served to other users (poisoning via unkeyed headers), one tenant's content served from another's cache, and cache deception (tricking the cache into storing a sensitive authenticated page). Design what goes into the cache key, what must be normalized or stripped, and the rules that keep the cache safe.