static ZooKeeperRegistrationSpec legacy(Endpoint endpoint) {
        return new LegacyZooKeeperRegistrationSpec(requireNonNull(endpoint, "endpoint"));
    }
Returns the {@link ZooKeeperRegistrationSpec} that registers the {@link Server} using the specified
{@link Endpoint}. The {@link Endpoint} is encoded to a comma-separated string whose format is
{@code <host>[:<port_number>[:weight]]}, such as:
<ul>
  <li>{@code "foo.com"} - default port number, default weight (1000)</li>
  <li>{@code "bar.com:8080} - port number 8080, default weight (1000)</li>
  <li>{@code "10.0.2.15:0:500} - default port number, weight 500</li>
  <li>{@code "192.168.1.2:8443:700} - port number 8443, weight 700</li>
</ul>
Note that the port number must be specified when you want to specify the weight.

@see ZooKeeperDiscoverySpec#legacy()
zookeeper3/src/main/java/com/linecorp/armeria/server/zookeeper/ZooKeeperRegistrationSpec.java