More simplification when using stubs in middleware tests
Describe how http sessions are currently handled

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extra : rebase_source : 5feea2e89ba7e902414c3c47dfd7e6cfbab9e4c1
Reveal unintended behaviour: session gets created as soon as application is accessed.

This needs to be fixed. Session should not be created until user adds to cart.
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Session only opens when required (i.e. when adding items to cart)
Locate cart in session when displaying content
Locate cart in session when selecting items for purchase
Locate cart in session when checking out
Provide cart to cashier when placing an order
We only create sessions when required (that is, when items are first added to cart)
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Eliminate duplication when accessing cart in session