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/test/java/org/elasticsearch/xpack/security/cli/HttpCertificateCommandTests.java
false,
            List.of("Certificate Signing Request"),
            Stream.of(password, csrName).filter(s -> "".equals(s) == false).collect(Collectors.toList())
        );
    }
    public void testGenerateSingleCertificateWithExistingCA() throws Exception {
        final Path outFile = testRoot.resolve("certs.zip").toAbsolutePath();
        final List<String> hostNames = randomHostNames();
        final List<String> ipAddresses = randomIpAddresses();
        final String certificateName = hostNames.get(0);
        final Path caCertPath = getDataPath("ca.crt");
        assertThat(caCertPath, isRegularFile());
        final Path caKeyPath = getDataPath("ca.key");
        assertThat(caKeyPath, isRegularFile());
        final String caPassword = CA_PASSWORD;
        final int years = randomIntBetween(1, 8);
        final HttpCertificateCommand command = new PathAwareHttpCertificateCommand(outFile);
        final MockTerminal terminal = MockTerminal.create();
        terminal.addTextInput(randomBoolean() ? "n" : ""); 
        terminal.addTextInput("y"); 
        
        switch (randomFrom(FileType.PEM_CERT, FileType.PEM_KEY, FileType.PKCS12)) {
            case PEM_CERT -> {
                terminal.addTextInput(caCertPath.toAbsolutePath().toString());
                terminal.addTextInput(caKeyPath.toAbsolutePath().toString());
            }
            case PEM_KEY -> {
                terminal.addTextInput(caKeyPath.toAbsolutePath().toString());
                terminal.addTextInput(caCertPath.toAbsolutePath().toString());
            }