flexprice/flexprice ? reverse-engineered prompt

Build me an open source billing platform for SaaS and AI products that can handle usage based pricing, credit based plans, and hybrid subscriptions.

I want to be able to send in usage events from my app or agent, have them processed in real time, and automatically turn that into meters, entitlements, invoices, and customer balances. It should support things like prepaid credits, top ups, free tiers, overages, seat based plans, and feature access limits. I also want a simple admin style UI where I can set up plans, pricing rules, customers, credits, and see usage and billing activity clearly.

Please make it self hosted but ready to run in the cloud too, with a clean API first design and good docs so I can integrate it with my product and with payment tools like Stripe. If you need current docs or examples, look them up online and follow the project’s existing patterns.