Feature #8388: Add DNS over TLS for upstream forwarders to the DNS Resolver
Add DNS over TLS checkbox for Domain Override entries
forward-tls-upstream in a forward-zone will trigger unbound to send queries to that server using SSL/TLS. Since we added an option for the '.' zone forwarding to use SSL/TLS in #8388, it makes sense to add the same option to domain overrides as well.
Some care will be needed when crafting the forward-addr lines since domain overrides may already specify a port, and we'll need to default that to 853 for TLS.