Update product API (#11)

* Update README to include go-swagger installation instructions

* Update product API

* Generate types

* Add `APIOnly` field to `ProductOffer` model

* Add additional fields to ProductPrice model

Author: Jonezzyboy

README.md

@@ -37,4 +37,13 @@ Use Fortifi
 
 	fmt.Printf("Customers First Name is %s\n", response.Payload.FirstName)
 
+```
+
+## Prerequisite: Install go-swagger
+
+Before generating code, ensure you have the correct tap for go-swagger:
+
+```sh
+brew tap go-swagger/go-swagger
+brew install go-swagger
 ```