Ask HN: Recommendation for an API / self-hosted software for user preferences

Hello

I am in the process of learning to create a mobile application, and would like to copy / move the user settings (typical settings screen with few options like theme name, etc) to a DB / API on the server. Instead of rolling out my own DB backed api, are there any open source recommendations ?

also - im self-learning these things, so any better approaches / standards for this is appreciated as well.

Cheers & happy holidays .. :)