observer progress, added to schema and added schema_observer class

source/core/object/repository.cpp

@@ -22,6 +22,8 @@ utils::result<void, utils::error> repository::detach(const node_ptr &node) {
 
   remove_node(node);
 
+  node->on_detach();
+
   return utils::ok<void>();
 }
 
@@ -126,6 +128,8 @@ utils::result<repository::node_ptr, utils::error> repository::attach_node(const
   nodes_by_name_.insert({node->name(), node});
   nodes_by_type_.insert({node->type_index(), node});
 
+  node->on_attach();
+
   return utils::ok(node);
 }