Test modification of a task by an on-add hook (test case for #3416) (#3443)

* Add test case to cover https://github.com/GothenburgBitFactory/taskwarrior/issues/3416

* Add (builtin) on-add-modify test hook and use it

* TDB2::add() move hook invocation before save (#3416)

src/TDB2.cpp

@@ -81,6 +81,9 @@ void TDB2::add (Task& task)
   std::string uuid = task.get ("uuid");
   changes[uuid] = task;
 
+  // run hooks for this new task
+  Context::getContext ().hooks.onAdd (task);
+
   auto innertask = replica.import_task_with_uuid (uuid);
 
   {
@@ -121,9 +124,6 @@ void TDB2::add (Task& task)
   // update the cached working set with the new information
   _working_set = std::make_optional (std::move (ws));
 
-  // run hooks for this new task
-  Context::getContext ().hooks.onAdd (task);
-
   if (id.has_value ()) {
       task.id = id.value();
   }