feat: add bookmark_notes to proto and DataSource with auto-delete on unbookmark

Co-Authored-By: Claude <noreply@anthropic.com>

core/datastore-proto/src/main/proto/com/google/samples/apps/nowinandroid/data/user_preferences.proto

@@ -49,5 +49,8 @@ message UserPreferences {
 
     bool use_dynamic_color = 19;
 
-    // NEXT AVAILABLE ID: 21
+    // Key: news resource ID, Value: note text
+    map<string, string> bookmark_notes = 21;
+
+    // NEXT AVAILABLE ID: 22
 }

core/datastore/src/main/kotlin/com/google/samples/apps/nowinandroid/core/datastore/NiaPreferencesDataSource.kt

@@ -128,6 +128,7 @@ class NiaPreferencesDataSource @Inject constructor(
                         bookmarkedNewsResourceIds.put(newsResourceId, true)
                     } else {
                         bookmarkedNewsResourceIds.remove(newsResourceId)
+                        bookmarkNotes.remove(newsResourceId)
                     }
                 }
             }
@@ -136,6 +137,26 @@ class NiaPreferencesDataSource @Inject constructor(
         }
     }
 
+    suspend fun setBookmarkNote(newsResourceId: String, note: String) {
+        try {
+            userPreferences.updateData {
+                it.copy { bookmarkNotes.put(newsResourceId, note) }
+            }
+        } catch (ioException: IOException) {
+            Log.e("NiaPreferences", "Failed to update bookmark note", ioException)
+        }
+    }
+
+    suspend fun removeBookmarkNote(newsResourceId: String) {
+        try {
+            userPreferences.updateData {
+                it.copy { bookmarkNotes.remove(newsResourceId) }
+            }
+        } catch (ioException: IOException) {
+            Log.e("NiaPreferences", "Failed to remove bookmark note", ioException)
+        }
+    }
+
     suspend fun setNewsResourceViewed(newsResourceId: String, viewed: Boolean) {
         setNewsResourcesViewed(listOf(newsResourceId), viewed)
     }

core/datastore/src/test/kotlin/com/google/samples/apps/nowinandroid/core/datastore/NiaPreferencesDataSourceTest.kt

@@ -86,4 +86,7 @@ class NiaPreferencesDataSourceTest {
         subject.setDynamicColorPreference(true)
         assertTrue(subject.userData.first().useDynamicColor)
     }
+
+    // TODO(Task 2): Add tests for setBookmarkNote, removeBookmarkNote, and
+    // bookmarkNotes auto-delete on unbookmark once UserData exposes bookmarkNotes.
 }