Add support for CheckoutSession on Discount

src/Stripe.net/Entities/Discounts/Discount.cs

@@ -6,24 +6,48 @@ namespace Stripe
 
     public class Discount : StripeEntity<Discount>, IHasId, IHasObject
     {
+        /// <summary>
+        /// Unique identifier for the object.
+        /// </summary>
         [JsonProperty("id")]
         public string Id { get; set; }
 
+        /// <summary>
+        /// String representing the object's type. Objects of the same type share the same value.
+        /// </summary>
         [JsonProperty("object")]
         public string Object { get; set; }
 
+        /// <summary>
+        /// The Checkout session that this coupon is applied to, if it is applied to a particular
+        /// session in payment mode. Will not be present for subscription mode.
+        /// </summary>
+        [JsonProperty("checkout_session")]
+        public string CheckoutSession { get; set; }
+
+        /// <summary>
+        /// Hash describing the coupon applied to create this discount.
+        /// </summary>
         [JsonProperty("coupon")]
         public Coupon Coupon { get; set; }
 
         #region Expandable Customer
 
+        /// <summary>
+        /// (ID of the Customer)
+        /// The ID of the customer associated with this discount.
+        /// </summary>
         [JsonIgnore]
         public string CustomerId
         {
             get => this.InternalCustomer?.Id;
             set => this.InternalCustomer = SetExpandableFieldId(value, this.InternalCustomer);
         }
 
+        /// <summary>
+        /// (Expanded)
+        /// The ID of the customer associated with this discount.
+        /// </summary>
         [JsonIgnore]
         public Customer Customer
         {
@@ -36,28 +60,53 @@ public Customer Customer
         internal ExpandableField<Customer> InternalCustomer { get; set; }
         #endregion
 
+        /// <summary>
+        /// Whether this object is deleted or not.
+        /// </summary>
         [JsonProperty("deleted", NullValueHandling = NullValueHandling.Ignore)]
         public bool? Deleted { get; set; }
 
+        /// <summary>
+        /// If the coupon has a <c>duration</c> of <c>repeating</c>, the date that this discount
+        /// will end. If the coupon has a <c>duration</c> of <c>once</c> or forever, this attribute
+        /// will be null.
+        /// </summary>
         [JsonProperty("end")]
         [JsonConverter(typeof(UnixDateTimeConverter))]
         public DateTime? End { get; set; }
 
+        /// <summary>
+        /// The invoice that the discount’s coupon was applied to, if it was applied directly to a
+        /// particular invoice.
+        /// </summary>
         [JsonProperty("invoice")]
         public string Invoice { get; set; }
 
+        /// <summary>
+        /// The invoice item id (or invoice line item id for invoice line items of
+        /// type=‘subscription’) that the discount’s coupon was applied to, if it was applied
+        /// directly to a particular invoice item or invoice line item.
+        /// </summary>
         [JsonProperty("invoice_item")]
         public string InvoiceItem { get; set; }
 
         #region Expandable PromotionCode
 
+        /// <summary>
+        /// (ID of the PromotionCode)
+        /// The promotion code applied to create this discount.
+        /// </summary>
         [JsonIgnore]
         public string PromotionCodeId
         {
             get => this.InternalPromotionCode?.Id;
             set => this.InternalPromotionCode = SetExpandableFieldId(value, this.InternalPromotionCode);
         }
 
+        /// <summary>
+        /// (Expanded)
+        /// The promotion code applied to create this discount.
+        /// </summary>
         [JsonIgnore]
         public PromotionCode PromotionCode
         {
@@ -70,19 +119,32 @@ public PromotionCode PromotionCode
         internal ExpandableField<PromotionCode> InternalPromotionCode { get; set; }
         #endregion
 
+        /// <summary>
+        /// Date that the coupon was applied.
+        /// </summary>
         [JsonProperty("start")]
         [JsonConverter(typeof(UnixDateTimeConverter))]
         public DateTime? Start { get; set; }
 
         #region Expandable Subscription
 
+        /// <summary>
+        /// (ID of the Subscription)
+        /// The subscription that this coupon is applied to, if it is applied to a particular
+        /// subscription.
+        /// </summary>
         [JsonIgnore]
         public string SubscriptionId
         {
             get => this.InternalSubscription?.Id;
             set => this.InternalSubscription = SetExpandableFieldId(value, this.InternalSubscription);
         }
 
+        /// <summary>
+        /// (Expanded)
+        /// The subscription that this coupon is applied to, if it is applied to a particular
+        /// subscription.
+        /// </summary>
         [JsonIgnore]
         public Subscription Subscription
         {