Add support for PendingUpdate and ProrationBehavior on Subscription APIs.

src/Stripe.net/Entities/Subscriptions/Subscription.cs

@@ -45,9 +45,24 @@ public class Subscription : StripeEntity<Subscription>, IHasId, IHasMetadata, IH
         [JsonConverter(typeof(DateTimeConverter))]
         public DateTime? CancelAt { get; set; }
 
+        /// <summary>
+        /// If the subscription has been canceled with the <c>AtPeriodEnd</c> flag
+        /// set to true, <c>CancelAtPeriodEnd</c> on the subscription will be true.
+        /// You can use this attribute to determine whether a subscription that
+        /// has a status of active is scheduled to be canceled at the end of
+        /// the current period.
+        /// </summary>
         [JsonProperty("cancel_at_period_end")]
         public bool CancelAtPeriodEnd { get; set; }
 
+        /// <summary>
+        /// If the subscription has been canceled, the date of that
+        /// cancellation. If the subscription was canceled with
+        /// <c>CancelAtPeriodEnd</c>, <c>CanceledAt</c> will still reflect the
+        /// date of the initial cancellation request, not the end of the
+        /// subscription period when the subscription is automatically moved to
+        /// a canceled state.
+        /// </summary>
         [JsonProperty("canceled_at")]
         [JsonConverter(typeof(DateTimeConverter))]
         public DateTime? CanceledAt { get; set; }
@@ -281,6 +296,13 @@ public SetupIntent PendingSetupIntent
         internal ExpandableField<SetupIntent> InternalPendingSetupIntent { get; set; }
         #endregion
 
+        /// <summary>
+        /// If specified, deferred upgrade changes that will be applied to the
+        /// subscription once the latest_invoice has been paid.
+        /// </summary>
+        [JsonProperty("pending_update")]
+        public SubscriptionPendingUpdate PendingUpdate { get; set; }
+
         /// <summary>
         /// Plan the customer is subscribed to. Only set if the subscription contains a single plan.
         /// </summary>

src/Stripe.net/Entities/Subscriptions/SubscriptionPendingUpdate.cs

@@ -0,0 +1,52 @@
+namespace Stripe
+{
+    using System;
+    using System.Collections.Generic;
+    using Newtonsoft.Json;
+    using Stripe.Infrastructure;
+
+    public class SubscriptionPendingUpdate : StripeEntity<SubscriptionPendingUpdate>
+    {
+        /// <summary>
+        /// If the update is applied, determines the date of the first full
+        /// invoice, and, for plans with <c>month</c> or year <c>intervals</c>,
+        /// the day of the month for subsequent invoices.
+        /// </summary>
+        [JsonProperty("billing_cycle_anchor")]
+        [JsonConverter(typeof(DateTimeConverter))]
+        public DateTime? BillingCycleAnchor { get; set; }
+
+        /// <summary>
+        /// The point after which the changes reflected by this update will be
+        /// discarded and no longer applied.
+        /// </summary>
+        [JsonProperty("expires_at")]
+        [JsonConverter(typeof(DateTimeConverter))]
+        public DateTime? ExpiresAt { get; set; }
+
+        /// <summary>
+        /// List of subscription items, each with an attached plan, that will
+        /// be set if the update is applied.
+        /// </summary>
+        [JsonProperty("subscription_items")]
+        public StripeList<SubscriptionItem> SubscriptionItems { get; set; }
+
+        /// <summary>
+        /// Unix timestamp representing the end of the trial period the
+        /// customer will get before being charged for the first time, if the
+        /// update is applied.
+        /// </summary>
+        [JsonProperty("trial_end")]
+        [JsonConverter(typeof(DateTimeConverter))]
+        public DateTime? TrialEnd { get; set; }
+
+        /// <summary>
+        /// Indicates if a <see cref="Plan" />’s <c>TrialPeriodDays</c> should
+        /// be applied to the subscription. Setting <see cref="TrialEnd" /> per
+        /// subscription is preferred, and this defaults to false. Setting this
+        /// flag to true together with trial_end is not allowed.
+        /// </summary>
+        [JsonProperty("trial_from_plan")]
+        public bool TrialFromPlan { get; set; }
+    }
+}

src/Stripe.net/Services/Invoices/UpcomingInvoiceOptions.cs

@@ -101,6 +101,17 @@ public class UpcomingInvoiceOptions : BaseOptions
         [JsonProperty("subscription_prorate")]
         public bool? SubscriptionProrate { get; set; }
 
+        /// <summary>
+        /// Determines how to handle
+        /// <a href="https://stripe.com/docs/billing/subscriptions/billing-cycle#prorations">prorations</a>
+        /// when the billing cycle changes. The value defaults to
+        /// <c>create_prorations</c>, indicating that proration invoice items
+        /// should be created. Prorations can be disabled by setting the value
+        /// to <c>none</c>.
+        /// </summary>
+        [JsonProperty("subscription_proration_behavior")]
+        public string SubscriptionProrationBehavior { get; set; }
+
         /// <summary>
         /// If previewing an update to a subscription, and doing proration,
         /// <c>subscription_proration_date</c> forces the proration to be calculated as though the

src/Stripe.net/Services/SubscriptionItems/SubscriptionItemCreateOptions.cs

@@ -42,6 +42,17 @@ public class SubscriptionItemCreateOptions : BaseOptions, IHasMetadata
         [JsonProperty("prorate")]
         public bool? Prorate { get; set; }
 
+        /// <summary>
+        /// Determines how to handle
+        /// <a href="https://stripe.com/docs/billing/subscriptions/billing-cycle#prorations">prorations</a>
+        /// when the billing cycle changes. The value defaults to
+        /// <c>create_prorations</c>, indicating that proration invoice items should
+        /// be created. Prorations can be disabled by setting the value to
+        /// <c>none</c>.
+        /// </summary>
+        [JsonProperty("proration_behavior")]
+        public string ProrationBehavior { get; set; }
+
         /// <summary>
         /// If set, the proration will be calculated as though the subscription was updated at the
         /// given time. This can be used to apply the same proration that was previewed with the

src/Stripe.net/Services/SubscriptionItems/SubscriptionItemUpdateOptions.cs

@@ -49,6 +49,17 @@ public class SubscriptionItemUpdateOptions : BaseOptions, IHasMetadata
         [JsonProperty("prorate")]
         public bool? Prorate { get; set; }
 
+        /// <summary>
+        /// Determines how to handle
+        /// <a href="https://stripe.com/docs/billing/subscriptions/billing-cycle#prorations">prorations</a>
+        /// when the billing cycle changes. The value defaults to
+        /// <c>create_prorations</c>, indicating that proration invoice items should
+        /// be created. Prorations can be disabled by setting the value to
+        /// <c>none</c>.
+        /// </summary>
+        [JsonProperty("proration_behavior")]
+        public string ProrationBehavior { get; set; }
+
         /// <summary>
         /// If set, the proration will be calculated as though the subscription was updated at the
         /// given time. This can be used to apply the same proration that was previewed with the

src/Stripe.net/Services/Subscriptions/SubscriptionCreateOptions.cs

@@ -180,6 +180,17 @@ public class SubscriptionCreateOptions : BaseOptions, IHasMetadata
         [JsonProperty("prorate")]
         public bool? Prorate { get; set; }
 
+        /// <summary>
+        /// Determines how to handle
+        /// <a href="https://stripe.com/docs/billing/subscriptions/billing-cycle#prorations">prorations</a>
+        /// when the billing cycle changes. The value defaults to
+        /// <c>create_prorations</c>, indicating that proration invoice items
+        /// should be created. Prorations can be disabled by setting the value
+        /// to <c>none</c>.
+        /// </summary>
+        [JsonProperty("proration_behavior")]
+        public string ProrationBehavior { get; set; }
+
         [Obsolete("Use Items")]
         [JsonProperty("quantity")]
         public long? Quantity { get; set; }

src/Stripe.net/Services/Subscriptions/SubscriptionUpdateOptions.cs

@@ -160,6 +160,17 @@ public class SubscriptionUpdateOptions : BaseOptions, IHasMetadata
         [JsonProperty("prorate")]
         public bool? Prorate { get; set; }
 
+        /// <summary>
+        /// Determines how to handle
+        /// <a href="https://stripe.com/docs/billing/subscriptions/billing-cycle#prorations">prorations</a>
+        /// when the billing cycle changes. The value defaults to
+        /// <c>create_prorations</c>, indicating that proration invoice items
+        /// should be created. Prorations can be disabled by setting the value
+        /// to <c>none</c>.
+        /// </summary>
+        [JsonProperty("proration_behavior")]
+        public string ProrationBehavior { get; set; }
+
         /// <summary>
         /// If set, the proration will be calculated as though the subscription
         /// was updated at the given time. This can be used to apply exactly