Change the way to create a new item in a shopping cart

[TimothyXu]

As a system administrator I need to have a nested API So that our service can be used intuitively as a RESTful service

Details and Assumptions

• Per the professor, use POST /shopcarts/{customer_id}/items, giving the {item_id, item_name, price, quantity}
• There is no need for the -1 dummy item for the empty shopcarts.

• Acceptance Criteria

  Given {customer_id} is a valid customer_id
  And {item_id, item_name, price, quantity} is valid
  And shopcart with id {customer_id} does not have item with id {item_id}
  When we call POST on /shopcarts/{customer_id}/items passing in {item_id, item_name, price, quantity}
  Then service returns code 201 CREATED

[TimothyXu]

Updated name to item_name to conform to our current schema

[kdokm]

@TimothyXu The tests may be affected by the change of common functions due to -1 issue. I will finish it later tonight so that you can get the latest version.

[TimothyXu]

no hurry. currently no problems.