chore(marketingFeatures): make marketingFeatures optional

Author: thoven87

Sources/StripeKit/Products/Products/Product.swift

@@ -45,7 +45,7 @@ public struct Product: Codable {
     /// A URL of a publicly-accessible webpage for this product.
     public var url: String?
     /// The marketing feature name. Up to 80 characters long.
-    public var marketingFeatures: [MarketingFeature]
+    public var marketingFeatures: [MarketingFeature]?
 
     public init(id: String,
                 active: Bool? = nil,
@@ -64,7 +64,7 @@ public struct Product: Codable {
                 unitLabel: String? = nil,
                 updated: Date? = nil,
                 url: String? = nil,
-                marketingFeatures: [MarketingFeature] = []) {
+                marketingFeatures: [MarketingFeature]? = []) {
         self.id = id
         self.active = active
         self._defaultPrice = Expandable(id: defaultPrice)