Add flag for automatic back pagination feature

libraries/matrix/impl/src/main/kotlin/io/element/android/libraries/matrix/impl/RustMatrixClientFactory.kt

@@ -105,6 +105,11 @@ class RustMatrixClientFactory(
     suspend fun create(client: Client): RustMatrixClient {
         val (anonymizedAccessToken, anonymizedRefreshToken) = client.session().anonymizedTokens()
 
+        // Must be called before creating the sync service, timelines etc.
+        if (featureFlagService.isFeatureEnabled(FeatureFlags.AutomaticBackPagination)) {
+            client.enableAutomaticBackpagination()
+        }
+
         client.setUtdDelegate(UtdTracker(analyticsService))
 
         val syncService = client.syncService()