If we can't crawl the content, we can't index it. The best way to index staging sites is to whitelist our crawler. The easiest way to do this is to look for "Sajaribot" at the start of the user-agent.
Restricting to IP is difficult given we use Google Cloud and have a very large and dynamic address range. But you can do this by downloading their blocks here.
If this is too difficult, you can always index your production site and search the index from your production site. This has no performance issues and will not change the search functionality on your site. This method allows the UI to be developed without the need for us to index your staging site.