* Update ObjectSerializer::toQueryValue method
It looks a bit ugly right now, but at least all tests has been passed.
* Add tests of query serialization
I used fixtures from OpenAPISpec main doc. Some prop combinations are not
officially documented yet, for instance behavior for nested objects and
arrays.
* Add test fixture from @nadar
* Add tests of Guzzle query build failure
* Add query build wrapper static method
Co-authored-by: Yuriy Belenko <yura-bely@mail.ru>