[SymfonyValidator] @Assert\Valid() does not work

[patrykbaszak]

Currently, validation works correctly, i.e. it always validates nested values, but the original Symfony Validator does not - nested objects are only validated if the parent had @Assert\Valid() attributes. Therefore, it needs improvement.

In a call to the init() method of the SymfonyValidator modifier, we can create a list of all properties that can be validated, and then use the modifyPropertyExpression() method to check if that property is on that list.