I agree that being able to support other auth providers would be a great improvement. As things stand now, though, Auth0 and Okta are still the only options hardcoded into the Fauna service as auth providers. Those are the ones we’ve tested against, and those are the ones we know will work, so those are the two we’ve made available in the service.
Ideally yes, we would love to be able to support any and all auth providers, including home grown ones. But auth misconfigurations can lead to all kinds of pain, including getting accounts locked out, so we have to be cognizant of that danger and put in appropriate guardrails to prevent it from happening.
We do have a roadmap item to extend this functionality so that developers can roll their own auth provider. We can’t say for sure when that will be available, though, as it’s dependent on some other features being completed, first.