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/HttpCertificateCommand.java
final String fileName = path == null ? "" : path.getFileName().toString().toLowerCase(Locale.ROOT);
        if (fileName.endsWith(".p12") || fileName.endsWith(".pfx") || fileName.endsWith(".pkcs12")) {
            return FileType.PKCS12;
        }
        if (fileName.endsWith(".jks")) {
            return FileType.JKS;
        }
        
        
        
        try (InputStream in = Files.newInputStream(path)) {
            byte[] leadingBytes = new byte[2];
            final int read = in.read(leadingBytes);
            if (read < leadingBytes.length) {
                
                return FileType.UNRECOGNIZED;
            }
            if (Arrays.equals(leadingBytes, MAGIC_BYTES1_PKCS12)
                || Arrays.equals(leadingBytes, MAGIC_BYTES2_PKCS12)
                || Arrays.equals(leadingBytes, MAGIC_BYTES2_JDK16_PKCS12)) {
                return FileType.PKCS12;
            }
            if (Arrays.equals(leadingBytes, MAGIC_BYTES_JKS)) {
                return FileType.JKS;
            }
        } catch (IOException e) {