I have a website under development, and I would like to grant time limited access to the site for people that I manually select and approve. I'm looking for an IDP or IDP abstraction layer that would enable me to do such a thing seamlessly. The functionality I'm looking for is that I can click a button (or something equally simple), generate a OTP which is valid for a certain period of time, and distribute this OTP to whomever I want to grant access. I've seen plenty of enterprise web applications with authorization flows like this, but I haven't been able to find open source authorization software (e.g. Keycloak) that supports such a mode. Is there something out there that does what I'm looking for?