• bugfix: fixed #173 - the Client.php was comparing the $rr->type value to "SOA" but should have been using the new ENUM value.
• changed from mt_rand() to random_int(); provides the same value, but faster and produces less complaints from code scanners about
  weak RNG, even though it doesn't actually matter since this isn't used for cryptography.
• realpath() the resolv.conf and private key file path just-in-case; this isn't a real problem.
• changed the resolver cache to use sha256 instead of md5(); again, this isn't cryptographic, so it doesn't matter, but in my testing
  the sha256 function is surprisingly slightly faster than md5(), and it kills the complaints from code scanners.
• dropped the use of curl_close(); it's deprecated as of PHP 8.5.
• cleaned up the BitMap::arrayToBitMap() function, and created a phpunit test to confirm it's working.
• changed any isset() cases to use === to avoid "loose comparison" warnings.