private static Allocation ofHostname(HostName hostName) {
            return new Allocation(hostName.value(), Optional.empty(), Optional.empty());
        }
Allocate an IPv4 address. A successful allocation is guaranteed to have an IPv4 address.

@param ipAddress Unassigned IPv4 address
@param resolver DNS name resolver to use
@return An allocation containing 1 IPv4 address.
node-repository/src/main/java/com/yahoo/vespa/hosted/provision/node/IP.java