If the user is currently looking at a product the reserve modal will assume that the customer wants to reserve the current product in store.
Shopping Cart Context
If the user is currently NOT looking at a product and a shopping cart is available, the the reserve modal will assume that the customer wants to reserve their entire cart in-store.
showChooseLocationModal()
Opens the "Choose Location" modal so the shopper can choose their preferred location that the app can default to from now on.
Example: Custom link to open the choose location modal.