Messaging: Implement per conversation channels. Update API level to 28.

* Get rid of in-app settings for notifications, replaced by channels features
* Remove all the notification plumbing and dead code

Test: m, manual

Signed-off-by: Luca Stefani <luca.stefani.ge1@gmail.com>
Signed-off-by: Joey <joey@lineageos.org>
Signed-off-by: Danny Baumann <dannybaumann@web.de>
Signed-off-by: Arne Coucheron <arco68@gmail.com>
Signed-off-by: Lyubo <lyubodzhamov@gmail.com>
Change-Id: Idb39ca32751d40b3376934775d2119dd6cc7e297

src/com/android/messaging/datamodel/action/DeleteConversationAction.java

@@ -35,6 +35,7 @@ import com.android.messaging.datamodel.MessagingContentProvider;
 import com.android.messaging.sms.MmsUtils;
 import com.android.messaging.util.Assert;
 import com.android.messaging.util.LogUtil;
+import com.android.messaging.util.NotificationsUtil;
 import com.android.messaging.widget.WidgetConversationProvider;
 
 import java.util.ArrayList;
@@ -118,6 +119,10 @@ public class DeleteConversationAction extends Action implements Parcelable {
                         + " has an invalid telephony thread id; will delete messages individually");
                 deleteConversationMessagesFromTelephony();
             }
+
+            // Finally, remove the conversation specific notification channel
+            NotificationsUtil.deleteNotificationChannel(Factory.get().getApplicationContext(),
+                    conversationId);
         } else {
             LogUtil.e(TAG, "DeleteConversationAction: conversationId is empty");
         }