stub in new shop_location and inventory models testing CodeRabbit

I need some new models for keeping track of shop locations and I need a way to keep track of phyical product inventory per phyical location

Summary by CodeRabbit

• New Features

  • Introduced handling options for physical products in the cart.
  • Added dynamic "next" input fields for smoother navigation post-login and verification.

• Bug Fixes

  • Improved error messages and invoice handling in the cart checkout process.

• Improvements

  • Enhanced readability and clarity of messages and error handling across multiple views.
  • Simplified return statements in coupon views for better code readability.

• Routes

  • Added new routes for managing cart options, viewing invoices, shop locations, and product inventory.