Avoid calling getSerializableData()

[SOHELAHMED7]

Fixes #81

This PR requires cebe/php-openapi#228 to be merged first.

[cebe]

changing the behavior of required and nullable is a major breaking change, if we want to do that we should do it before 2.0 stable release. Also need to check how that affects our spec in layer5.

[SOHELAHMED7]

Also need to check how that affects our spec in layer5

I will check this PR in L5 to see how much spec there requires change

[SOHELAHMED7]

As I mentioned in #81 (comment), getSerializableData() is used for 2 things:

1. resolving properties
2. faker generation

While fixing 2nd, I found that 1st might be fixed without introducing breaking change if a change is introduced upstream library cebe/php-openapi. This change is required for 2nd.

Change is to introduce a public property in cebe\openapi\SpecBaseObject and cebe\openapi\spec\Reference class which will hold raw spec data. Example:

namespace cebe\openapi;

abstract class SpecBaseObject implements SpecObjectInterface, DocumentContextInterface
{
+   public $rawSpec;
    public function __construct(array $data)
    {
+       $this->rawSpec = $data;

Though I still recommend to introduce breaking change and make this library more and more spec compliant.

Example usage: 9538035

Implementation in upstream lib: cebe/php-openapi#228