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
throw userException;
            }
            final Map<String, Object> responseMap = enrollResponse.getResponseBody();
            if (responseMap == null) {
                UserException userException = new UserException(
                    ExitCodes.DATA_ERROR,
                    "Aborting enrolling to cluster. Empty response when calling the enroll node API (" + enrollNodeUrl + ")"
                );
                try {
                    deleteDirectory(tempGeneratedTlsCertsDir);
                } catch (Exception ex) {
                    userException.addSuppressed(ex);
                }
                throw userException;
            }
            final List<String> missingFields = new ArrayList<>();
            final String httpCaKeyPem = (String) responseMap.get("http_ca_key");
            if (Strings.isNullOrEmpty(httpCaKeyPem)) {
                missingFields.add("http_ca_key");
            }
            final String httpCaCertPem = (String) responseMap.get("http_ca_cert");
            if (Strings.isNullOrEmpty(httpCaCertPem)) {
                missingFields.add("http_ca_cert");
            }
            final String transportKeyPem = (String) responseMap.get("transport_key");
            if (Strings.isNullOrEmpty(transportKeyPem)) {
                missingFields.add("transport_key");
            }
            final String transportCaCertPem = (String) responseMap.get("transport_ca_cert");
            if (Strings.isNullOrEmpty(transportCaCertPem)) {