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
assertThat(zipRoot.resolve("ca"), not(pathExists()));
        verifyKibanaDirectory(
            zipRoot,
            true,
            List.of("2. elasticsearch-ca.pem"),
            Stream.of(password, caPassword, caKeyPath.getFileName().toString())
                .filter(s -> "".equals(s) == false)
                .collect(Collectors.toList())
        );
    }
    public void testGenerateMultipleCertificateWithNewCA() throws Exception {
        final Path outFile = testRoot.resolve("certs.zip").toAbsolutePath();
        final int numberCerts = randomIntBetween(3, 6);
        final String[] certNames = new String[numberCerts];
        final String[] hostNames = new String[numberCerts];
        for (int i = 0; i < numberCerts; i++) {
            certNames[i] = randomAlphaOfLengthBetween(6, 12);
            hostNames[i] = randomAlphaOfLengthBetween(4, 8);
        }
        final HttpCertificateCommand command = new PathAwareHttpCertificateCommand(outFile);
        final MockTerminal terminal = MockTerminal.create();
        terminal.addTextInput(randomBoolean() ? "n" : ""); 
        terminal.addTextInput(randomBoolean() ? "n" : ""); 
        final String caDN;
        final int caYears;
        final int caKeySize;
        
        if (randomBoolean()) {
            terminal.addTextInput("y");