added sent and id column again for add_cam_main

id checks if entry already exists. sent says if the entry is already
sent to the db

lib/interfaces/i_db.dart

@@ -9,7 +9,7 @@ abstract interface class IDb {
 
   Future<int> addMainEntry(Map<String, String> excursion);
 
-  Future<void> updateMainEntry(Map<String, String> excursion);
+  Future<int> updateMainEntry(Map<String, String> excursion);
 
   Future<void> updateSent(int id);