Adding discount metadata to sessions

{
    "amount": 20000,
    "items": [
        {
            "id": "item-1",
            "vat": 25,
            "amount": 10000,
            "line_id": "1",
            "quantity": 1,
            "description": "Item 1",
            "discount_lines": [
                {
                    "amount": 2000,
                    "line_id": 1,
                    "description": "Manually added 20 kroner off. // Original price 12000",
                    "discount_id": "manual-20-kroner-off",
                    "discount_type": "manual"
                }
            ]
        },
        {
            "id": "item-2",
            "vat": 25,
            "amount": 10000,
            "line_id": "2",
            "quantity": 2,
            "description": "Item 2",
            "discount_lines": [
                {
                    "amount": 2500,
                    "line_id": 1,
                    "percentage": 20,
                    "description": "New customer 20% on item 2. // Original price 12500", 
                    "discount_id": "new-customer-20-item-2",
                    "discount_type": "customer"
                }
            ]
        }
    ]
}

{
    "amount": 20000,
    "items": [
        {
            "id": "item-1",
            "vat": 25,
            "amount": 10000,
            "line_id": "1",
            "quantity": 1,
            "description": "Item 1"
        },
        {
            "id": "item-2",
            "vat": 25,
            "amount": 10000,
            "line_id": "2",
            "quantity": 2,
            "description": "Item 2"
        }
    ],
    "discount_lines": [
        {
            "amount": 5000,
            "line_id": "dl1",
            "percentage": 20,
            "description": "20% off on the first order // The original sum was 25000",
            "discount_id": "first-order-20-percent",
            "discount_type": "customer"
        }
    ]
}