Add more TimestampConverters

Author: solid-maksymtielnyi

lib/messages.g.dart

@@ -59,6 +59,7 @@ class CreatePreviewInvoiceSubscriptionDetailsRequest {
   /// before the current period ends, this will cause a proration if prorations
   /// have been enabled using proration_behavior. If set during a future period,
   /// this will always cause a proration for that period.
+  @TimestampConverter()
   final DateTime? cancelAt;
 
   /// Indicate whether this subscription should cancel at the end of the current
@@ -93,6 +94,7 @@ class CreatePreviewInvoiceSubscriptionDetailsRequest {
   final DateTime? prorationDate;
 
   /// Date a subscription is intended to start (can be future or past).
+  @TimestampConverter()
   final DateTime? startDate;
 
   /// If provided, the invoice returned will preview updating or creating a

lib/src/messages/requests/create_invoice_preview_request.dart

@@ -41,6 +41,7 @@ class CreateSubscriptionRequest {
   /// start date to. If set, the first invoice will contain a proration for the
   /// timespan between the start date and the current time. Can be combined with
   /// trials and the billing cycle anchor.
+  @TimestampConverter()
   final DateTime? backdateStartDate;
 
   /// A future timestamp in UTC format to anchor the subscription’s billing
@@ -60,6 +61,7 @@ class CreateSubscriptionRequest {
   /// before the current period ends, this will cause a proration if prorations
   /// have been enabled using proration_behavior. If set during a future period,
   /// this will always cause a proration for that period.
+  @TimestampConverter()
   final DateTime? cancelAt;
 
   /// The tax rates that will apply to any subscription item that does not have
@@ -89,6 +91,7 @@ class CreateSubscriptionRequest {
   /// override the default trial period of the plan the customer is being
   /// subscribed to. The special value now can be provided to end the customer’s
   /// trial immediately. Can be at most two years from billing_cycle_anchor.
+  @TimestampConverter()
   final DateTime? trialEnd;
 
   /// Indicates if a plan’s trial_period_days should be applied to the