Add Totals to CartItemInterface

[pmclain]

Description (*)

Fixed Issues (if relevant)

1. Cart items doesn't contain information about prices #633

Manual testing scenarios (*)

1. Create empty cart
2. Add cart items
3. Query cart and request item totals

{
  cart(cart_id: "{{cartId}}") {
    items {
      prices {
        price {
          value
          currency
        }
        row_total {
          value
          currency
        }
        row_total_including_tax {
          value
          currency
        }
      }
    }
    prices {
      grand_total {
        value
        currency
      }
      subtotal_including_tax {
        value
        currency
      }
      subtotal_excluding_tax {
        value
        currency
      }
      subtotal_with_discount_excluding_tax {
        value
        currency
      }
      applied_taxes {
        label
        amount {
          value
          currency
        }
      }
    }
  }
}

Contribution checklist (*)

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• All automated tests passed successfully (all builds on Travis CI are green)

[TomashKhamlai]

@pmclain, could you please merge mainline to this PR?

[pmclain]

@TomashKhamlai mainline merged d26dbbc

[lenaorobei]

@magento run all tests

[lenaorobei]

@paliarush please approve schema changes.

[magento-engcom-team]

Hi @lenaorobei, thank you for the review.
ENGCOM-5576 has been created to process this Pull Request
✳️ @lenaorobei, could you please add one of the following labels to the Pull Request?

Label	Description
Auto-Tests: Covered	All changes in Pull Request is covered by auto-tests
Auto-Tests: Not Covered	Changes in Pull Request requires coverage by auto-tests
Auto-Tests: Not Required	Changes in Pull Request does not require coverage by auto-tests

[ghost]

Hi @pmclain, thank you for your contribution!
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[keharper]

Schema changes documented in 2.3.4 as a result of work done by the internal development team.