Add P24 confirm payment functionality for web integration (#2004)

packages/stripe_js/lib/src/api/payment_intents/confirm_p24_payment_data.dart

@@ -0,0 +1,34 @@
+import 'package:freezed_annotation/freezed_annotation.dart';
+import 'package:stripe_js/stripe_api.dart';
+
+part 'confirm_p24_payment_data.freezed.dart';
+part 'confirm_p24_payment_data.g.dart';
+
+@freezed
+class ConfirmP24PaymentData with _$ConfirmP24PaymentData {
+  const factory ConfirmP24PaymentData({
+    /// Either the ID of an existing PaymentMethod, or an object containing
+    /// data to create a PaymentMethod with.
+    ///
+    /// This is required to process the payment. If you already have a PaymentMethod
+    /// attached to the PaymentIntent, you do not need to specify this field.
+    ///
+    /// See the official Stripe documentation for additional details:
+    /// https://stripe.com/docs/payments/p24
+    @paymentMethodDetailJsonKey P24PaymentMethodDetails? paymentMethod,
+
+    /// The url your customer will be directed to after they complete authentication.
+    @JsonKey(name: "return_url") String? returnUrl,
+
+    /// To set up a SEPA Direct Debit payment method using the bank details
+    ///  from this P24 payment, set this parameter to off_session.
+    /// When using this parameter, a customer will need to be set on the
+    /// PaymentIntent. The newly created SEPA Direct Debit PaymentMethod
+    /// will be attached to this customer.
+    @JsonKey(name: "setup_future_usage")
+    PaymentIntentSetupFutureUsage? setupFutureUsage,
+  }) = _ConfirmP24PaymentData;
+
+  factory ConfirmP24PaymentData.fromJson(Map<String, dynamic> json) =>
+      _$ConfirmP24PaymentDataFromJson(json);
+}

packages/stripe_js/lib/src/api/payment_intents/confirm_p24_payment_options.dart

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+import 'package:freezed_annotation/freezed_annotation.dart';
+
+part 'confirm_p24_payment_options.freezed.dart';
+part 'confirm_p24_payment_options.g.dart';
+
+@freezed
+class ConfirmP24PaymentOptions with _$ConfirmP24PaymentOptions {
+  const factory ConfirmP24PaymentOptions({
+    /// Set this to false if you want to manually handle
+    /// the authorization redirect. Default is true.
+    @Default(true) bool? handleActions,
+  }) = _ConfirmP24PaymentOptions;
+
+  factory ConfirmP24PaymentOptions.fromJson(Map<String, dynamic> json) =>
+      _$ConfirmP24PaymentOptionsFromJson(json);
+}