Implement start of backups payment integration work.

donations/lib/src/main/java/org/signal/donations/InAppPaymentType.kt

@@ -0,0 +1,41 @@
+/*
+ * Copyright 2024 Signal Messenger, LLC
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+package org.signal.donations
+
+import org.signal.core.util.Serializer
+
+enum class InAppPaymentType(val code: Int, val recurring: Boolean) {
+  /**
+   * Used explicitly for mapping DonationErrorSource. Writing this value
+   * into an InAppPayment is an error.
+   */
+  UNKNOWN(-1, false),
+
+  /**
+   * This payment is for a gift badge
+   */
+  ONE_TIME_GIFT(0, false),
+
+  /**
+   * This payment is for a one-time donation
+   */
+  ONE_TIME_DONATION(1, false),
+
+  /**
+   * This payment is for a recurring donation
+   */
+  RECURRING_DONATION(2, true),
+
+  /**
+   * This payment is for a recurring backup payment
+   */
+  RECURRING_BACKUP(3, true);
+
+  companion object : Serializer<InAppPaymentType, Int> {
+    override fun serialize(data: InAppPaymentType): Int = data.code
+    override fun deserialize(input: Int): InAppPaymentType = entries.first { it.code == input }
+  }
+}

donations/lib/src/main/java/org/signal/donations/StripeApi.kt

@@ -62,9 +62,9 @@ class StripeApi(
     data class Failure(val reason: Throwable) : CreatePaymentSourceFromCardDataResult()
   }
 
-  fun createSetupIntent(sourceType: PaymentSourceType.Stripe): Single<CreateSetupIntentResult> {
+  fun createSetupIntent(inAppPaymentType: InAppPaymentType, sourceType: PaymentSourceType.Stripe): Single<CreateSetupIntentResult> {
     return setupIntentHelper
-      .fetchSetupIntent(sourceType)
+      .fetchSetupIntent(inAppPaymentType, sourceType)
       .map { CreateSetupIntentResult(it) }
       .subscribeOn(Schedulers.io())
   }
@@ -588,6 +588,7 @@ class StripeApi(
 
   interface SetupIntentHelper {
     fun fetchSetupIntent(
+      inAppPaymentType: InAppPaymentType,
       sourceType: PaymentSourceType.Stripe
     ): Single<StripeIntentAccessor>
   }