HTTP/HTTPS mixed content errors #612 (#613)

* Configure TrustProxies middleware
* Add trusted proxies to deps
* Replace jquery request with axios request code
* Trust current user IP for forwarded headers
* Update dependencies
* Downgrade self-updater package for PHP 7.2

app/Models/FlightField.php

@@ -9,6 +9,7 @@ use App\Contracts\Model;
  *
  * @property string name
  * @property string slug
+ * @property bool   required
  */
 class FlightField extends Model
 {