Load mappings from classes

[nilportugues]

Create a new loading method, as asked by many in the Laravel community, using classes.

The haljson.php file in config/ dir loads the classes in an array, this gets parsed and then cached producing the same results as now.

Good thing about this approach is that mappings can sit with code instead of sitting in the configuration side.

---

use Acme\Domain\Dummy\Post;

class PostModelMapping extends ApiMapping
{
     public function getClass() {
         return Post::class;
    }

     public function getAlias() {
         return "";
    }

     public function getIdProperties() {
         return ['postId'];
    }

     public function getAliasedProperties() {
         return [
           'author' => 'author',
            'title' => 'headline',
            'content' => 'body',
         ];
    }

     public function getHideProperties() {
         return [];
    }

   //etc....
}

[nilportugues]

Can be counted as done.

Will be supported as as soon as nilportugues/php-api-transformer@b209041 is integrated into this package...which requires Laravel Eloquel Models easy hack to get it working perfectly.