We generate certificates that are intended to be used for server authentication in a couple of places:

- `bin/elasticsearch-certutil http` command  ( See `CertGenUtils.generateSignedCertificate` in `HttpCertificateCommand` )
- TLS auto-configuraion for node startup ( see [`AutoConfigureNode`](https://github.com/elastic/elasticsearch/blob/814f7f9f52cb8c05db6465b9bfc818ea5d76c575/x-pack/plugin/security/cli/src/main/java/org/elasticsearch/xpack/security/cli/AutoConfigureNode.java#L454) )

In these cases we know that the certificate is meant to be used for server authentication, so we can set Extended Key Usage extension to `1.3.6.1.5.5.7.3.1`
x-pack/plugin/security/cli/src/main/java/org/elasticsearch/xpack/security/cli/AutoConfigureNode.java
import org.elasticsearch.cli.ProcessInfo;
import org.elasticsearch.cli.Terminal;
import org.elasticsearch.cli.UserException;
import org.elasticsearch.cluster.coordination.ClusterBootstrapService;
import org.elasticsearch.cluster.node.DiscoveryNode;
import org.elasticsearch.cluster.node.DiscoveryNodeRole;
import org.elasticsearch.common.Strings;
import org.elasticsearch.common.UUIDs;
import org.elasticsearch.common.cli.EnvironmentAwareCommand;
import org.elasticsearch.common.network.InetAddresses;
import org.elasticsearch.common.network.NetworkAddress;
import org.elasticsearch.common.network.NetworkService;
import org.elasticsearch.common.network.NetworkUtils;
import org.elasticsearch.common.settings.KeyStoreWrapper;
import org.elasticsearch.common.settings.SecureString;
import org.elasticsearch.common.settings.Settings;
import org.elasticsearch.core.CheckedConsumer;
import org.elasticsearch.core.Nullable;
import org.elasticsearch.core.PathUtils;
import org.elasticsearch.core.SuppressForbidden;
import org.elasticsearch.discovery.DiscoveryModule;
import org.elasticsearch.discovery.SettingsBasedSeedHostsProvider;
import org.elasticsearch.env.Environment;
import org.elasticsearch.http.HttpTransportSettings;
import org.elasticsearch.transport.TransportSettings;
import org.elasticsearch.xcontent.XContentType;
import org.elasticsearch.xpack.core.XPackSettings;
import org.elasticsearch.xpack.core.security.CommandLineHttpClient;
import org.elasticsearch.xpack.core.security.EnrollmentToken;
import org.elasticsearch.xpack.core.security.HttpResponse;