Fix nested navigation graphs

Change-Id: I2c3ad0a0f6c132230b821d3621389913cf37247c

app/src/main/java/com/google/samples/apps/nowinandroid/navigation/NiaNavHost.kt

@@ -54,13 +54,11 @@ fun NiaNavHost(
         )
         interestsGraph(
             navigateToTopic = { navController.navigate("${TopicDestination.route}/$it") },
-            navigateToAuthor = { navController.navigate("${AuthorDestination.route}/$it") }
-        )
-        topicGraph(
-            onBackClick = { navController.popBackStack() }
-        )
-        authorGraph(
-            onBackClick = { navController.popBackStack() }
+            navigateToAuthor = { navController.navigate("${AuthorDestination.route}/$it") },
+            nestedGraphs = {
+                topicGraph(onBackClick = { navController.popBackStack() })
+                authorGraph(onBackClick = { navController.popBackStack() })
+            }
         )
     }
 }

feature-interests/src/main/java/com/google/samples/apps/nowinandroid/feature/interests/navigation/InterestsNavigation.kt

@@ -18,6 +18,7 @@ package com.google.samples.apps.nowinandroid.feature.interests.navigation
 
 import androidx.navigation.NavGraphBuilder
 import androidx.navigation.compose.composable
+import androidx.navigation.navigation
 import com.google.samples.apps.nowinandroid.core.navigation.NiaNavigationDestination
 import com.google.samples.apps.nowinandroid.feature.interests.InterestsRoute
 
@@ -28,12 +29,20 @@ object InterestsDestination : NiaNavigationDestination {
 
 fun NavGraphBuilder.interestsGraph(
     navigateToTopic: (String) -> Unit,
-    navigateToAuthor: (String) -> Unit
+    navigateToAuthor: (String) -> Unit,
+    nestedGraphs: NavGraphBuilder.() -> Unit
+
 ) {
-    composable(route = InterestsDestination.route) {
-        InterestsRoute(
-            navigateToTopic = navigateToTopic,
-            navigateToAuthor = navigateToAuthor,
-        )
+    navigation(
+        route = InterestsDestination.route,
+        startDestination = InterestsDestination.destination
+    ) {
+        composable(route = InterestsDestination.destination) {
+            InterestsRoute(
+                navigateToTopic = navigateToTopic,
+                navigateToAuthor = navigateToAuthor,
+            )
+        }
+        nestedGraphs()
     }
 }