public SslContextBuilder withKeyManager(X509ExtendedKeyManager keyManager) {
        this.keyManager = keyManager;
        return this;
    }
Note: Callee is responsible for configuring the key manager.
      Any keystore configured by {@link #withKeyStore(KeyStore, char[])} or the other overloads will be ignored.
security-utils/src/main/java/com/yahoo/security/SslContextBuilder.java