in src/main/java/com/spotify/github/v3/clients/JwtTokenIssuer.java [53:62]
public static JwtTokenIssuer fromPrivateKey(final byte[] privateKey)
throws NoSuchAlgorithmException, InvalidKeySpecException {
KeySpec keySpec = PKCS1PEMKey.loadKeySpec(privateKey)
.orElseGet(() -> new PKCS8EncodedKeySpec(privateKey));
KeyFactory kf = KeyFactory.getInstance("RSA");
PrivateKey signingKey = kf.generatePrivate(keySpec);
return new JwtTokenIssuer(signingKey);
}