Add 'private_key_bits' option to EC key generation (#630)

Documented the addition of the 'private_key_bits' option with a comment clarifying its non-standard usage for EC keys.

Author: Spomky

src/Library/Core/Util/ECKey.php

@@ -92,6 +92,7 @@ private static function createECKeyUsingOpenSSL(string $curve): array
         $key = openssl_pkey_new([
             'curve_name' => self::getOpensslCurveName($curve),
             'private_key_type' => OPENSSL_KEYTYPE_EC,
+            'private_key_bits' => 2048, // Not used for EC keys. See https://github.com/php/php-src/pull/19103
         ]);
         if ($key === false) {
             throw new RuntimeException('Unable to create the key');