Spring Boot services: authentication, product catalogue and Stripe payments

Three Java and Spring Boot services built as part of Scaler’s Full Stack Development program, covering the backend pieces most web apps need.

Authentication service ([code](https://www.twine.net/signin sign-up, login, logout and token validation, BCrypt password hashing, 24-hour JWTs backed by session records, Spring Authorization Server.

Product catalogue service ([code](https://www.twine.net/signin REST API on MySQL with Flyway schema migrations, Redis caching, and OAuth2 resource-server security that checks role claims.

Payment service ([code](https://www.twine.net/signin creates Stripe payment links behind a PaymentGateway interface (strategy pattern), so a second provider can be added without touching callers, and verifies signed Stripe webhooks.

Stack: Java, Spring Boot, Spring Security, Spring Data JPA, MySQL, Flyway, Redis, OAuth2/JWT, Stripe.