Per Origin Host Header Override

Introduced the ability to override the Host header on a per-origin basis within Cloudflare's Load Balancing solution. This feature addresses issues where third-party applications (e.g., Heroku, S3) require specific origin hostnames that differ from the end-user's requested domain. The override is applied to both the request to the origin and its associated health monitor. Restrictions are in place to ensure the override is a valid 'Host' header, a single FQDN or IP address resolvable by public DNS, and a subdomain of an account-associated zone.