Add CollectionMethod to InvoiceUpdateOptions

src/Stripe.net/Enums/Billing.cs

@@ -1,10 +1,15 @@
 namespace Stripe
 {
+    using System;
     using System.Runtime.Serialization;
     using Newtonsoft.Json;
     using Newtonsoft.Json.Converters;
 
-    // Deprecated. Please use CollectionMethod
+    /// <summary>
+    /// The field this enum was used for has been renamed to
+    /// <c>CollectionMethod</c> and now accepts string.
+    /// </summary>
+    [Obsolete("Use CollectionMethod instead")]
     [JsonConverter(typeof(StringEnumConverter))]
     public enum Billing
     {

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

@@ -19,6 +19,13 @@ public class InvoiceUpdateOptions : BaseOptions
         [JsonProperty("auto_advance")]
         public bool? AutoAdvance { get; set; }
 
+        /// <summary>
+        /// Either <c>charge_automatically</c> or <c>send_invoice</c>. This
+        /// field can be updated only on <c>draft</c> invoices.
+        /// </summary>
+        [JsonProperty("collection_method")]
+        public string CollectionMethod { get; set; }
+
         /// <summary>
         /// A list of up to 4 custom fields to be displayed on the invoice.
         /// </summary>

src/Stripe.net/Services/SubscriptionSchedules/SubscriptionScheduleSharedOptions.cs

@@ -34,6 +34,7 @@ public abstract class SubscriptionScheduleSharedOptions : BaseOptions
         [JsonProperty("default_source")]
         public string DefaultSourceId { get; set; }
 
+        /// <summary>
         /// Either <c>charge_automatically</c>, or <c>send_invoice</c>. When
         /// charging automatically, Stripe will attempt to pay the underlying
         /// subscription at the end of each billing cycle using the default