Can delete conversation messages

lib/helpers/conversations_helper.dart

@@ -320,6 +320,27 @@ class ConversationsHelper {
     return SendMessageResult.SUCCESS;
   }
 
+  /// Delete permanently a message specified by its [id]
+  Future<bool> deleteMessage(int id) async {
+
+    // Delete the message online
+    final response = await APIRequest(
+      uri: "conversations/deleteMessage",
+      needLogin: true,
+      args: {
+        "messageID": id.toString()
+      }
+    ).exec();
+
+    if(response.code != 200) return false;
+
+
+    // Delete the message locally
+    return await _conversationMessagesDatabaseHelper.delete(id);
+
+  }
+
+
   /// Turn an API response into a ConversationMessage object
   ConversationMessage _apiToConversationMessage({
     @required int conversationID,