I was building backend in java spring along with full authentication authorization flow but after some time I realized what if the user forgets password how to reset it and many more questions.
After a bit of google searching came across firebase authentication , OKTA, AUTH0 the later 2 seems expensive.
So what do you use for your needs?
If they use Rails, they probably use Devise...
If they use Laravel, they probably use Passport...
I'm certain most indiehackers are using these open source solutions.