Add FQDN/domain support for outbound firewall destination rules

Please add support for outbound firewall rules where the destination can be specified by FQDN/hostname, not only by static IP address.

Our server needs to make outbound requests to api.openai.com. The issue is that OpenAI does not publish a stable destination IP range for api.openai.com. The hostname is stable, but uses the cloudflare edge network, so IPs change all the time.

We have a similar issue with other services we use where their FQDN points to an IP range, and we have to get the support to add the range, as we cant do that through the Spanel firewall rules panel ourselves.