public static function mergeCSPList(array $cspList)
    {
        $finalCSP = [];

        foreach ($cspList as $csp)
        {
            foreach ($csp as $directive => $sources)
            {
                if ( ! isset($finalCSP[$directive]))
                {
                    $finalCSP[$directive] = $sources;

                    continue;
                }
                elseif ($finalCSP[$directive] === true)
                {
                    continue;
                }
                else
                {
                    $finalCSP[$directive] = array_merge(
                        $finalCSP[$directive],
                        $sources
                    );

                    continue;
                }
            }
        }

        return $finalCSP;
    }