Symfony 5 support

Added Symfony 5 support and fixed PHPUnit deprecation errors

Fix deprecation warnings

Fixed The Symfony\Component\EventDispatcher\Event::stopPropagation method is deprecated (since Symfony 4.3, use "Symfony\Contracts\EventDispatcher\Event" instead) warning

First release!

Features:

1. Authorization check
2. Validation rules
3. Possibility to change data before validation with FormRequest::validationData method