Filter error array by unique values

[paul-stolk-webdiensten]

Description (*)

Added an array_unique to prevent duplicate errors.

Fixed Issues (if relevant)

1. graphql-input provides to Customer as many errors as appeared instead of last one like on Magento Storefront magento/graphql-ce#416: graphql-input provides to Customer as many errors as appeared instead of last one like on Magento Storefront graphql-input provides to Customer as many errors as appeared instead of last one like on Magento Storefront magento/graphql-ce#416

Manual testing scenarios (*)

1. Create a product with two or more required customizable options
2. Add the product with GraphQl to the cart, with for example:

mutation {
  addSimpleProductsToCart(
    input: {
      cart_id: "5qqnw42QYVX5SIHRFHETKhDQfb0mDe5K"
      cart_items: [
        {
          data: {
            quantity: 1
            sku: "416"
          }
        }
      ]
    }
  ) {
    cart {
      items {
        id
        product {
          sku
          stock_status
        }
        quantity
      }
    }
  }
}

Questions or comments

Contribution checklist (*)

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