[Feature]: Extendable showcase-SDK for Showcase application

[kpanot]

Context

To demonstrate the SDK generation we have generated a "simple" SDK based on the PetStore to be used inside the Showcase application.

The issue we have is that, for storage purpose, we have manually generated an ID on top of the Pet model in the application which is the actual scope of the "Extendable" SDK

Proposal

• Create a Extendable Showcase SDK
• Extend the Pet model to turn the id as mandatory and generate it at revive time
• Integrate this SDK in the Showcase application