Thanks! This is good feedback. The guide is effectively a verbose walkthrough setting up OAuth Proxy, which is the only way you could add authorization to a pre-existing application outside of your control, for example Prometheus.

For new projects, it might seem like picking up built-in auth system is easier until you realize you have to build a model of hierarchies of organizations, groups, etc... In my experience, some of these libraries cannot even express that model despite it being the most commonly required for web apps. ShareWith implements that model for you and even handles some of the trickier corner-cases like arbitrarily nesting groups.