feat: allow client certificates on NSI

[eduardoperetto]

This feature enables mutual authentication when loading NSI/NSA files for discoveries.

In order to use it, you need to set the following properties on config/params.php file:

   'certificate.use_client_cert' => true,
    'certificate.filename' => "client_cert.pem",
    'certificate.keyfile' => "client_key.pem",	
    'certificate.pass' => "your_password",	
    'certificate.ca_file' => "ca_cert.pem",