[FEATURE] Additional Restful Json Request instead Form-Data Requests

[devmes]

This pull request adds the option to send data in json format instead of standard form-data. Prerequisite is that on the request the content type is set to "application / Json". If no content type has been specified, the form data can be sent as before.

Json Post Sample:

curl --request POST http://localhost/routing/extension-key/my/demo/product
{
    "newProduct": {
        "type":"sample",
        "title":"sample"
    }
}