Changes to GET /products/:product_product_id/messages

the items response's property type changed from no type to object for status 200

added the new optional query request parameter limit

added the new optional query request parameter offset

added the optional property items/auto to the response with the 200 status

added the optional property items/id to the response with the 200 status

added the optional property items/product to the response with the 200 status

added the required property items/external_id to the response with the 200 status

added the required property items/value to the response with the 200 status

endpoint added