Add MySQL SSL support

[matejzero]

We are using Pakiti with MySQL that only allows SSL connections. As far as I looked, that is not natively supported, but I managed to make it work by changing the connect function in https://github.com/CESNET/pakiti-server/blob/master/src/managers/DbManager.php#L130.

Changing $this->_dbLink = new mysqli(Config::$DB_HOST, Config::$DB_USER, Config::$DB_PASSWORD); to

$this->_dbLink = mysqli_init();
$this->_dbLink->real_connect(Config::$DB_HOST, Config::$DB_USER, Config::$DB_PASSWORD, NULL, NULL, NULL, MYSQLI_CLIENT_SSL );

worked for me.

But this will work if you don't have self-signed certs and must use SSL connection.

My knowledge of php is not good enough to produce a nice PR to add support for SSL. But if there is anyone that wants to implement this, a few config options would probably be needed:

• option to use SSL or not
• option to provide custom certs (key, cert and ca) and ciphers via ssl_set - optionally, if using signed certs, this is not needed
• option to not verify server certificate (MYSQLI_CLIENT_SSL_DONT_VERIFY_SERVER_CERT)