Specify a domain to allow as a source for the selected directive. This can be a fully qualified domain name, optionally with a scheme and/or port.

Valid formats include:

• example.com - Allow the domain (matches both HTTP and HTTPS)
• https://example.com - Allow only HTTPS from the domain
• example.com:8080 - Allow the domain on a specific port
• *.example.com - Allow all subdomains using a wildcard
• https://*.example.com - Allow all subdomains over HTTPS only

Note that wildcards can only be used as the leftmost subdomain (e.g., *.example.com is valid, but foo.*.example.com is not).