[Example]: RSC/SSR Cart with session

[juanpprieto]

Description

A hydrogen example demonstrating a 💯 .server-driven basic Cart workflow.

• Provides a set of cart utilities (getCart, createCart...) as well as a GraphQL cart client
• Provides a /api/cart/[action] that handle POST requests from the different get, create, add and remove form actions.
• Persists cartId and cartCount to the session (cookie), so they can be used used during the .server lifecycle
• Uses form actions for all interactions with the API. e.g — AddToCart, remove..
• Provides suspendedFn a utility to enable <Suspend /> friendly async API calls from .server components

Additional context

Oxygen Demo

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