private static boolean isAlphabeticOrDigit(char c) {
        return (c >= '0' && c <= '9') || (c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z');
    }
@author James Chen
@implSpec <a href="https://tools.ietf.org/html/rfc4515"> RFC 4515: String Representation of
          Search Filters</a>
turms-gateway/src/main/java/im/turms/gateway/infra/ldap/element/operation/search/Filter.java