Allow domain names in whitelist for IP address. (And rename whitelist to allowlist).
I have a server (app) on heroku. It has a domain name. I don't have a dedicated ip address range. But if I could put my domain name in (myapp.herokupapp.com or myapp.com if I get that name from godaddy), then when my server connects, you could do a DNS lookup of the domain names in the whitelist, and allow connection from those. And then, my app, and many others would be more secure. People could also use dynamic dns to support connections from their home computers, more securely.
I've seen some traffic about mongodb databases being hacked, though their security was weak, I think a quick effort on this could add a lot of security for a lot of people.
Security matters.