DefaultResponse constructors have hardcoded 200 status codes

[wafer-bw]

Taking from the example in this repository, we can see that this spec's response status code is incorrectly 200. Perhaps these constructors could accept a status code?

petstore-expanded.yaml

post:
  summary: Creates a new pet
  description: Creates a new pet in the store. Duplicates are allowed
  operationId: addPet
  requestBody:
    description: Pet to add to the store
    required: true
    content:
      application/json:
        schema:
          $ref: '#/components/schemas/NewPet'
  responses:
    '201':
      description: pet response
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/Pet'
    default:
      description: unexpected error
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/Error'

petstore.gen.go

// AddPetJSONDefaultResponse is a constructor method for a AddPet response.
// A *Response is returned with the configured status code and content type from the spec.
func AddPetJSONDefaultResponse(body Error) *Response {
	return &Response{
		body:        body,
		Code:        200,
		contentType: "application/json",
	}
}

[karitham]

We don't currently render Default responses as default cases. You can control status of the output response with Status, eg

return AddPetJSONDefaultResponse(Error{"sunturtle is not a valid pet}).Status(400)

If you feel like it warrants a special constructor, we are open to contributions, I am not opposed to the idea