Configure Lock template via Gitlab Deployments extension?


I am experimenting with the Gitlab Deployments extension for the first time. At the moment, I am trying to commit the proper json in the Git repository for the hosted login page to become active, configured to use the Lock HTML template.

I was able to make the page active by adding the file pages/login.json with this content:

   "enabled": true

But when I look in the Dashboard, the dropdown reads Default Templates and the HTML editor below it is empty.

What should I write to configure the Lock template via the Gitlab deployment extension? I want to prevent that I need to copy the content of the Lock template to the HTML file in my repo.