Dispose usage of #[Assert\Valid] attribute for nested objects analysis

[rela589n]

It would make much more sense not to depend on a third-party attribute, provided by sf validator #[Assert\Valid] for the main feature of the library.

[rela589n]

I guess the whole exceptional validation could be done w/o any additional attributes for ordinary properties (since we have ExceptionalValidation attribute on the top of the class. Currently, it's not all so simple with arrays, though. Since PHP doesn't yet have generics available, we can't be sure about iterable type, - therefore from the reflection point of view, it's not possible to know array type. Not that we can't check out what's in that array, - but it seems to be a dirty solution as for me

[rela589n]

Implemented the most straightforward solution - include everything iterable. #63

It's most likely that all these properties will have nested objects included for exceptional validation, since it's request-mapped object which must be validated. Thus, no need to check some generics or anything like it.