GraphQL-433: Prepare Quote GraphQL scheme for 2.3.1 release

Author: naydav

app/code/Magento/QuoteGraphQl/etc/schema.graphqls

@@ -7,8 +7,6 @@ type Query {
 
 type Mutation {
     createEmptyCart: String @resolver(class: "\\Magento\\QuoteGraphQl\\Model\\Resolver\\CreateEmptyCart") @doc(description:"Creates an empty shopping cart for a guest or logged in user")
-    applyCouponToCart(input: ApplyCouponToCartInput): ApplyCouponToCartOutput @resolver(class: "\\Magento\\QuoteGraphQl\\Model\\Resolver\\Coupon\\ApplyCouponToCart")
-    removeCouponFromCart(input: RemoveCouponFromCartInput): RemoveCouponFromCartOutput @resolver(class: "\\Magento\\QuoteGraphQl\\Model\\Resolver\\Coupon\\RemoveCouponFromCart")
     setShippingAddressesOnCart(input: SetShippingAddressesOnCartInput): SetShippingAddressesOnCartOutput @resolver(class: "\\Magento\\QuoteGraphQl\\Model\\Resolver\\SetShippingAddressesOnCart")
     applyCouponToCart(input: ApplyCouponToCartInput): ApplyCouponToCartOutput @resolver(class: "\\Magento\\QuoteGraphQl\\Model\\Resolver\\ApplyCouponToCart")
     removeCouponFromCart(input: RemoveCouponFromCartInput): RemoveCouponFromCartOutput @resolver(class: "\\Magento\\QuoteGraphQl\\Model\\Resolver\\RemoveCouponFromCart")
@@ -98,7 +96,6 @@ type ApplyCouponToCartOutput {
 }
 
 type Cart {
-    cart_id: String
     items: [CartItemInterface]
     applied_coupon: AppliedCoupon
     shipping_addresses: [CartAddress]! @resolver(class: "\\Magento\\QuoteGraphQl\\Model\\Resolver\\ShippingAddresses")