ServerListenOptions
Options to pass to method@Server.listen, etc.
%SOUP_SERVER_LISTEN_IPV4_ONLY and %SOUP_SERVER_LISTEN_IPV6_ONLY only make sense with method@Server.listen_all and method@Server.listen_local, not plain method@Server.listen (which simply listens on whatever kind of socket you give it). And you cannot specify both of them in a single call.