Every SaaS project starts the same way. You open a new Spring Boot project and the first three weeks look like this: Week 1: JWT auth, refresh tokens, BCrypt passwords Week 2: Stripe webhooks, subscription states, idempotency Week 3: Rate limiting, global error handling, API docs You haven't shipped a single feature yet. You've just rebuilt infrastructure you've built five times before. I got tired of it. So I spent two weeks building it once, properly, with tests, a...