Use Projects::CreateService to create imported projects so hooks are executed.

lib/gitlab/github_import/project_creator.rb

@@ -10,29 +10,16 @@ module Gitlab
       end
 
       def execute
-        @project = Project.new(
+        ::Projects::CreateService.new(current_user,
           name: repo.name,
           path: repo.name,
           description: repo.description,
-          namespace: namespace,
-          creator: current_user,
+          namespace_id: namespace.id,
           visibility_level: repo.private ? Gitlab::VisibilityLevel::PRIVATE : Gitlab::VisibilityLevel::PUBLIC,
           import_type: "github",
           import_source: repo.full_name,
           import_url: repo.clone_url.sub("https://", "https://#{current_user.github_access_token}@")
-        )
-
-        if @project.save!
-          @project.reload
-
-          if @project.import_failed?
-            @project.import_retry
-          else
-            @project.import_start
-          end
-        end
-
-        @project
+        ).execute
       end
     end
   end