Support stripe payment on Android (#6591)

Task/Issue URL:
https://app.asana.com/1/137249556945/task/1210380647876465?focus=true

### Description
Add support for showing stripe flow on Android

### Steps to test this PR
- [x] Apply patch attached in
https://app.asana.com/1/137249556945/project/1209991789468715/task/1210448620621729?focus=true
- [x] Fresh install
- [x] Sign in on grafana.duckduckgo.com
- [x] Go to Settings > Subscription Settings and change base URL to
https://charmston.duckduckgo.com/subscriptions
- [x] Close and open the app
- [x] Go to https://charmston.duckduckgo.com/pro?featurePage=stripe
- [x] You should see options to buy products, select one of them
- [x] Add testing details to purchase the subscription (see [Stripe
testing](https://docs.stripe.com/testing#testing-interactively))
- [x] Once purchase successful, check you are redirected to Welcome page
- [x] Go to Settings screen and check subscription features are visible
and available
- [x] Go to Settings > Subscription Settings and check the Free Trial is
active

### No UI changes

Author: nalcalag

subscriptions/subscriptions-impl/src/main/java/com/duckduckgo/subscriptions/impl/RealSubscriptions.kt

@@ -255,6 +255,9 @@ interface PrivacyProFeature {
 
     @Toggle.DefaultValue(DefaultFeatureValue.TRUE)
     fun useClientWithCacheForFeatures(): Toggle
+
+    @Toggle.DefaultValue(DefaultFeatureValue.TRUE)
+    fun supportsAlternateStripePaymentFlow(): Toggle
 }
 
 @ContributesBinding(AppScope::class)

subscriptions/subscriptions-impl/src/main/java/com/duckduckgo/subscriptions/impl/messaging/SubscriptionMessagingInterface.kt

@@ -407,9 +407,11 @@ class SubscriptionMessagingInterface @Inject constructor(
 
             val authV2Enabled = privacyProFeature.enableSubscriptionFlowsV2().isEnabled()
             val duckAiSubscriberModelsEnabled = privacyProFeature.duckAiPlus().isEnabled()
+            val supportsAlternateStripePaymentFlow = privacyProFeature.supportsAlternateStripePaymentFlow().isEnabled()
             val resultJson = JSONObject().apply {
                 put("useSubscriptionsAuthV2", authV2Enabled)
                 put("usePaidDuckAi", duckAiSubscriberModelsEnabled)
+                put("useAlternateStripePaymentFlow", supportsAlternateStripePaymentFlow)
             }
 
             val response = JsRequestResponse.Success(

subscriptions/subscriptions-impl/src/test/java/com/duckduckgo/subscriptions/impl/messaging/SubscriptionMessagingInterfaceTest.kt

@@ -822,13 +822,14 @@ class SubscriptionMessagingInterfaceTest {
         givenSubscriptionMessaging(enabled = true)
         givenAuthV2(enabled = true)
         givenDuckAiPlus(enabled = true)
+        givenStripeSupported(enabled = true)
 
         val expected = JsRequestResponse.Success(
             context = "subscriptionPages",
             featureName = "useSubscription",
             method = "getFeatureConfig",
             id = "myId",
-            result = JSONObject("""{"useSubscriptionsAuthV2":true,"usePaidDuckAi":true}"""),
+            result = JSONObject("""{"useSubscriptionsAuthV2":true,"usePaidDuckAi":true,"useAlternateStripePaymentFlow":true}"""),
         )
 
         val message = """
@@ -851,13 +852,14 @@ class SubscriptionMessagingInterfaceTest {
         givenSubscriptionMessaging(enabled = true)
         givenAuthV2(enabled = false)
         givenDuckAiPlus(enabled = true)
+        givenStripeSupported(enabled = true)
 
         val expected = JsRequestResponse.Success(
             context = "subscriptionPages",
             featureName = "useSubscription",
             method = "getFeatureConfig",
             id = "myId",
-            result = JSONObject("""{"useSubscriptionsAuthV2":false,"usePaidDuckAi":true}"""),
+            result = JSONObject("""{"useSubscriptionsAuthV2":false,"usePaidDuckAi":true,"useAlternateStripePaymentFlow":true}"""),
         )
 
         val message = """
@@ -880,13 +882,14 @@ class SubscriptionMessagingInterfaceTest {
         givenSubscriptionMessaging(enabled = true)
         givenAuthV2(enabled = true)
         givenDuckAiPlus(enabled = false)
+        givenStripeSupported(enabled = true)
 
         val expected = JsRequestResponse.Success(
             context = "subscriptionPages",
             featureName = "useSubscription",
             method = "getFeatureConfig",
             id = "myId",
-            result = JSONObject("""{"useSubscriptionsAuthV2":true,"usePaidDuckAi":false}"""),
+            result = JSONObject("""{"useSubscriptionsAuthV2":true,"usePaidDuckAi":false,"useAlternateStripePaymentFlow":true}"""),
         )
 
         val message = """
@@ -988,6 +991,12 @@ class SubscriptionMessagingInterfaceTest {
         whenever(privacyProFeature.duckAiPlus()).thenReturn(duckAiPlusToggle)
     }
 
+    private fun givenStripeSupported(enabled: Boolean) {
+        val stripeSupportedToggle = mock<com.duckduckgo.feature.toggles.api.Toggle>()
+        whenever(stripeSupportedToggle.isEnabled()).thenReturn(enabled)
+        whenever(privacyProFeature.supportsAlternateStripePaymentFlow()).thenReturn(stripeSupportedToggle)
+    }
+
     private fun checkEquals(expected: JsRequestResponse, actual: JsRequestResponse) {
         if (expected is JsRequestResponse.Success && actual is JsRequestResponse.Success) {
             assertEquals(expected.id, actual.id)