Fallback to the default push gateway on error (#5742)

* Add more HTTP response code returning NoMatrixGateway

Fix Push notifications with Mozilla's autopush that returns 406

* Update gateway resolver tests to match new known errors

* Use default gateway on error if no gateway is recorded yet

* Update gateway resolver tests to return default gateway on error

libraries/pushproviders/unifiedpush/src/main/kotlin/io/element/android/libraries/pushproviders/unifiedpush/UnifiedPushGatewayUrlResolver.kt

@@ -29,8 +29,9 @@ class DefaultUnifiedPushGatewayUrlResolver(
     ): String {
         return when (gatewayResult) {
             is UnifiedPushGatewayResolverResult.Error -> {
-                // Use previous gateway if any, or the provided one
-                unifiedPushStore.getPushGateway(instance) ?: gatewayResult.gateway
+                // Use previous gateway if any, or the default one
+                unifiedPushStore.getPushGateway(instance)
+                    ?: defaultPushGatewayHttpUrlProvider.provide()
             }
             UnifiedPushGatewayResolverResult.ErrorInvalidUrl,
             UnifiedPushGatewayResolverResult.NoMatrixGateway -> {

libraries/pushproviders/unifiedpush/src/test/kotlin/io/element/android/libraries/pushproviders/unifiedpush/DefaultUnifiedPushGatewayUrlResolverTest.kt

@@ -60,7 +60,7 @@ class DefaultUnifiedPushGatewayUrlResolverTest {
     }
 
     @Test
-    fun `resolve Error returns the url if no current url is available`() {
+    fun `resolve Error returns the default gateway url if no current url is available`() {
         val sut = createDefaultUnifiedPushGatewayUrlResolver(
             unifiedPushStore = FakeUnifiedPushStore(
                 getPushGatewayResult = { instance ->
@@ -73,7 +73,7 @@ class DefaultUnifiedPushGatewayUrlResolverTest {
             gatewayResult = UnifiedPushGatewayResolverResult.Error("aUrl"),
             instance = "instance",
         )
-        assertThat(result).isEqualTo("aUrl")
+        assertThat(result).isEqualTo(FakeDefaultPushGatewayHttpUrlProvider().provide())
     }
 
     private fun createDefaultUnifiedPushGatewayUrlResolver(